Techniques for placing medical leads for electrical stimulation of nerve tissue

ABSTRACT

This disclosure is directed to extra, intra, and transvascular medical lead placement techniques for arranging medical leads and electrical stimulation and/or sensing electrodes proximate nerve tissue within a patient.

This application claims the benefit of U.S. Provisional Application Nos.61/007,542, 61/007,543, 61/190,045, and 61/190,046, all of which werefiled Apr. 30, 2008, and the entire contents of each of which isincorporated herein by this reference.

TECHNICAL FIELD

The disclosure relates to medical devices and, more particularly,medical devices that deliver electrical stimulation therapy.

BACKGROUND

A wide variety of implantable medical devices (“IMD”) that delivertherapy to or monitor a physiologic condition of a patient have beenclinically implanted or proposed for clinical implantation in patients.Such devices may deliver therapy or monitor the heart, muscle, nerve,the brain, the stomach or other organs or tissues. In some cases, IMD'sdeliver electrical stimulation therapy and/or monitor physiologicalsignals via one or more electrodes or sensor elements, at least some ofwhich may be included as part of one or more elongated implantablemedical leads. Implantable medical leads may be configured to allowelectrodes or sensors to be positioned at desired locations for deliveryof stimulation or sensing electrical activity or other physiologicalparameters. For example, electrodes or sensors may be located at adistal portion of the lead. A proximal portion of the lead is coupled toan IMD housing, which contains electronic circuitry such as stimulationgeneration and/or sensing circuitry. In some cases, electrodes orsensors are positioned on an IMD housing as an alternative or inaddition to electrodes or sensors deployed on one or more leads.

One example IMD is an electrical stimulation device directed to nervetissue stimulation, which is sometimes referred to as an implantablenerve stimulator or implantable neurostimulator (“INS”). One particularapplication of nerve tissue stimulation is vagal nerve stimulation.Vagal nerve stimulation may provide therapeutic effects for heartfailure, as well as other conditions including, e.g., depression,epilepsy and various digestion conditions. Some vagal nerve stimulators,as well as nerve trunk stimulators in general, have employed cuffelectrodes to surround the nerve tissue and anchor the stimulator leadand/or electrodes within a patient. Cuff electrodes have somedisadvantages, however, including, that such electrodes requirerelatively invasive techniques for placing them within a patient. In thecase of vagal nerve stimulation, cuff electrodes require an incision inthe neck and dissection of the vagus from within the carotid sheath forplacement around the nerve. Additionally, cuff electrodes are known tocause lesions or otherwise damage the nerve tissue, which may lead todeleterious effects on nerve function, as well as the development ofscar tissue.

SUMMARY

In general, examples disclosed herein are directed to extra, intra, andtransvascular medical lead placement techniques for arranging medicalleads and electrical stimulation and/or sensing electrodes proximatenerve tissue within a patient.

In one example, an implantable medical lead system is configured todeliver electrical stimulation from within a lumen of a blood vesselwithin a patient to nerve tissue located adjacent to and outside of theblood vessel. The system includes a medical lead arranged within a lumenof the blood vessel. An electrode is connected toward a distal end ofthe lead adjacent the nerve tissue. An active fixation member isconfigured to anchor the lead to a wall of the blood vessel lumen.

In another example, a method includes deploying a lead through a lumenof a blood vessel to a target nerve tissue site. An electrode connectedto the lead is arranged within the blood vessel lumen adjacent the nervetissue. The lead is actively fixed to a wall of the blood vessel lumen.

The details of one or more examples according to this disclosure are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages will be apparent from the descriptionand drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a conceptual diagram illustrating an example therapy systemincluding an implantable medical device (IMD) that delivers cardiac andnerve tissue stimulation to a patient.

FIG. 1B is a conceptual diagram illustrating an example therapy systemincluding an implantable cardiac device (ICD) and an implantableneurostimulator (INS).

FIG. 2 is a functional block diagram of the IMD of FIG. 1A.

FIG. 3 is a functional block diagram of an example medical deviceprogrammer.

FIGS. 4 and 5 are schematic illustrations depicting relevant humananatomy for lead placement techniques described herein.

FIG. 6 is a schematic illustration depicting a medical lead placedextravascularly adjacent a vagus nerve.

FIG. 7 is a flow chart illustrating an example extravascular leadplacement method.

FIGS. 8A and 8B show two example sleeve anchors for use withextravascular lead placement techniques according to this disclosure.

FIG. 8C shows deployable lobe member for use with extravascular leadplacement techniques according to this disclosure.

FIG. 9 is a schematic illustration depicting a medical lead placedintravascularly within the internal jugular vein adjacent a vagus nerve.

FIG. 10 is a flow chart illustrating an example intravascular leadplacement method.

FIG. 11 is a schematic illustration of a two dimensional ultrasonicimage generated by a sensor used in conjunction with the intravascularlead placement arrangement shown in FIG. 9.

FIGS. 12A and 12B show several example deployment members for use inintravascular lead placement methods and systems according to thisdisclosure.

FIG. 13 is a schematic illustration depicting a medical lead placedintravascularly and actively fixed to a wall of the internal jugularvein adjacent a vagus nerve.

FIGS. 14A-14J are elevation front views of example anchors that may beused alone or in combination to anchor or bias a medical lead and/orelectrode placed in accordance with examples disclosed herein.

FIG. 15 is a schematic illustration depicting a cylindrical lead memberconnected to a medical lead placed intravascularly within the internaljugular vein adjacent a vagus nerve.

FIG. 16 is a flow chart illustrating an example method ofintravascularly placing the cylindrical lead member of FIG. 15.

FIGS. 17A and 17B are schematic illustrations of a cylindrical leadmember arranged within a delivery catheter.

FIGS. 18A-18D are schematic illustrations of different examples of acylindrical lead member that is expandable and contractible fordeployment and redeployment within a blood vessel.

FIG. 19 is a schematic illustration depicting a medical lead placedtransvascularly through a wall of the internal jugular toward a vagusnerve.

FIG. 20 is a flow chart illustrating an example transvascular leadplacement method.

FIGS. 21A-21D show several example deployment members for use intransvascular lead placement methods and systems according to thisdisclosure.

FIG. 22 shows one example of a deployment member that employs a guidemember constructed from a shape memory material.

FIGS. 23A and 23B illustrate example arrangements of electrode pairs inflanking, non-contacting relationship with a vagus nerve.

DETAILED DESCRIPTION

In general, this disclosure is directed toward techniques for placingmedical leads proximate nerve tissue within a patient for electricalstimulation of the tissue without the use of potentially deleteriouselectrode configurations including e.g., cuff electrodes. Techniquesdisclosed herein are also generally directed to flexible placementtechniques and structures that provide for one or more temporary leadplacements and stimulation tests, prior to chronically placing the leadswithin the patient for nerve tissue stimulation. Furthermore, techniquesaccording to this disclosure are adapted to enable minimally invasiveintroduction of the medical leads into the patient. Implantableelectrical stimulation systems and methods in accordance with thisdisclosure may be used to deliver therapy to patients suffering fromconditions that range from chronic pain, tremor, Parkinson's disease,and epilepsy, to urinary or fecal incontinence, sexual dysfunction,obesity, spasticity, and gastroparesis. Specific types of electricalstimulation therapies for treating such conditions include, e.g.,cardiac pacing, neurostimulation, muscle stimulation, or the like.

Systems disclosed generally include one or more medical leads adapted tobe placed within a patient proximate nerve tissue targeted forelectrical stimulation therapy. The leads include one or more electrodesthat are arranged toward a distal end of the leads. In some examples,the leads are anchored at least proximate the distal end of the leads byor according to one or more structures or techniques described in detailbelow. The medical leads are connected to an electrical stimulatorincluding a processor adapted to carry out the electrical stimulation ofthe target nerve tissue according to, e.g., one or more therapy programsstored in non-volatile memory. The electrical stimulator may include,generally, stimulation generation and/or sensing circuitry. In someexamples, the stimulator may also include circuitry for cardiac rhythmtherapy, e.g., one or more of pacing, cardioversion, and/ordefibrillation therapy, to a heart of a patient. The stimulator may belocated at a distance from the target tissue site and coupled to aproximal end of the leads. In another example, however, the electricalstimulator may include one or more electrodes or sensors on its housingor a member, element or structure coupled to the housing, may be placedin conjunction with the electrodes or sensors proximate the target nervetissue site, and may be powered by, e.g., battery or a remote powersource. In some examples, the electrical stimulator may be powered byradio frequency pulses delivered from either an external or asubcutaneously implanted RF transmitter to a receiver unit arranged withthe stimulator, lead, and/or electrodes. In other examples, some part ofthe stimulator, lead, or electrodes may be composed of a piezoelectricmaterial that can generate current when excited mechanically by ultrasound waves transmitted from an external or implanted source. In yetanother example, two separate implantable devices, e.g. an INS and acardiac therapy device are individually implanted and communicativelyconnected to one another. Placement of the leads and electrodesproximate the nerve tissue includes extravascular, intravascular, andtransvascular placement structures and techniques.

The techniques disclosed herein are described generally in the contextof stimulation of one of the vagus nerves on the vagal nerve trunk inthe neck of a human patient. Vagal nerve stimulation is useful intreating various conditions including, e.g., heart failure, depression,epilepsy, and various gastrointestinal conditions. However, the methodsand systems disclosed are also applicable to stimulation and treatmentof other nerve tissues that are located in diverse locations. Forexample, the disclosed techniques may be used in the stimulation of ahypoglossal nerve. In other examples, a nerve plexus that forms a nodeof intersecting nerves including, e.g., the cervical, brachial, lumbar,sacral, or solar plexus may be stimulated using methods and systemsaccording to this disclosure. Additionally, the techniques may be usedfor stimulation of nerve ganglia including, e.g., one or more ganglia ofa nerve plexus.

As an additional example, the techniques disclosed herein may be used inthe stimulation of vascular baroreceptors including, e.g., carotidbaroreceptors. Baroreceptors are sensors located in blood vessels thatdetect the pressure of blood flowing therethrough, and can send messagesto the central nervous system to increase or decrease total peripheralresistance and cardiac output. The receptors function by detecting theamount a blood vessel wall stretches, and sending a signal to thenervous system in response to the detected expansion of the vessel.Baroreceptors act as part of a negative feedback system called thebaroreflex that returns blood pressure to a normal level as soon asthere is a deviation from a typical pressure, such as, e.g., the meanarterial blood pressure.

Prior extravascular placement techniques have involved invasiveimplantation procedures because the target tissue, such as a vagus nervemust be dissected to place and anchor the leads proximate the nervetissue. Additionally, prior extravascular placement techniques commonlyincluded lead electrode fixation at the lead distal end using, e.g.,cuff electrodes, which may have deleterious effects over time including,e.g., nerve tissue necrosis. Techniques described herein provide forextravascular placement of medical leads for nerve tissue stimulationusing implantation procedures with reduced invasiveness and without theneed to anchor the leads at or very near their distal end. In general,the disclosed techniques include placing a portion of a medical leadhaving an electrode in an extravascular space within a sheath of tissuewithin a patient, and adjacent nerve tissue that is also within thesheath of tissue. The lead is anchored offset from the electrode atleast partially outside of the sheath. As used herein, the term sheathof tissue generally refers to constraining connective tissue that holdstogether different biological structures within the body of a patient(e.g., a common carotid sheath).

Intra or transvascular lead placement proximate the target nerve tissue,on the other hand, generally requires minimally invasive surgicaltechniques because the leads may be guided to the site through a bloodvessel, e.g., a vein or artery, that may be readily accessible, e.g.,transcutaneously through a small incision. Intra and transvascular leadplacement techniques described herein may facilitate placing the distalend of the lead in close proximity of the target nerve tissue, therelative position of which with respect to an adjacent blood vessel mayvary from patient-to-patient. Additionally, guided transvascular leadplacement as described herein may avoid safety risks of such proceduresincluding, e.g., piercing adjacent vessels, such as an artery.

Some example intravascular techniques include structures and methods fordeployment of one or more medical leads at a first location, testingstimulation at the first location, and, depending on the efficacy of thestimulation provided by electrodes on the leads at the first location,redeploying the leads to a second location. In one example, leadplacement is improved by locating target nerve tissue with a sensorincluding, e.g., an intravascular ultrasound (IVUS) imaging systemand/or measuring the efficacy of test electrical stimulation pulses froman electrode on the lead through a blood vessel adjacent the targettissue. After a placement location is determined, one or more leadsincluding one or more electrodes may be deployed into the vessel andanchored to a vessel wall near the target nerve tissue. In someexamples, the electrodes may be anchored with a fixation member thatactively engages tissue of the blood vessel wall. In anotherintravascular placement example, an expandable and contractiblegenerally cylindrical lead member is temporarily deployable for testingmultiple electrode locations and combinations before deploying themember for chronic stimulation of the target nerve tissue.

Transvascular techniques generally include improving lead placement bylocating target nerve tissue with a sensor including, e.g., an IVUSimaging system, through a blood vessel adjacent the target tissue. Aftera placement location is determined, one or more leads including one ormore electrodes may be deployed through the vessel wall and anchored tothe vessel wall or other tissue near the target nerve tissue.

The extra, intra, and transvascular lead placement techniques disclosedmay also benefit, in some examples, from electrode pairs arranged inflanking, non-contacting relationship with the target nerve tissue. Inone example, multiple leads are arranged longitudinally on opposingsides of the target nerve tissue, and include electrodes innon-contacting relationship with the target nerve tissue. In anotherexample, one lead that includes multiple electrodes is employed suchthat at least two of the electrodes are arranged in flanking,non-contacting relationship with the target nerve tissue. Such flanking,non-contacting electrode arrangements may provide one or more anode andcathode electrode combinations for electrical stimulation across thetarget nerve tissue without the deleterious effects of tissue contactingtechniques, such as may be caused by cuff electrodes.

FIG. 1A is a conceptual diagram illustrating an example therapy system10 that provides cardiac rhythm therapy and nerve tissue stimulationtherapy to patient 12. Therapy system 10 includes implantable medicaldevice (IMD) 16, which is connected (or “coupled”) to leads 18, 20, 22,28, and programmer 24. IMD 16 may be subcutaneously or submuscularlyimplanted in the body of a patient 12 (e.g., in a chest cavity, lowerback, lower abdomen, or buttocks of patient 12).

IMD 16 may include a cardiac therapy module (not shown in FIG. 1A) and aneurostimulation module (not shown in FIG. 1A) enclosed within outerhousing 44. The cardiac therapy module may generate and deliver cardiacrhythm management therapy to heart 14 of patient 12, and may include,for example, an implantable pacemaker, cardioverter, and/ordefibrillator that provide therapy to heart 14 of patient 12 viaelectrodes coupled to one or more of leads 18, 20, and 22. In someexamples, the cardiac therapy module may deliver pacing pulses, but notcardioversion or defibrillation pulses, while in other examples, thecardiac therapy module may deliver cardioversion or defibrillationpulses, but not pacing pulses. In addition, in further examples, cardiactherapy module may deliver pacing, cardioversion, and defibrillationpulses. IMD 16 may deliver pacing that includes one or both ofanti-tachycardia pacing (ATP) and cardiac resynchronization therapy(CRT).

The neurostimulation module of IMD 16 may include a signal generatorthat generates and delivers electrical stimulation to a tissue site ofpatient 12, e.g., tissue proximate a vagus nerve or other target nervetissue of patient 12. In some examples, the tissue site may include aperipheral nerve. As previously indicated, in some examples, the tissuesite may include a nerve plexus that forms a node of intersecting nervesincluding, e.g., the cervical, brachial, lumbar, sacral, or solarplexus. Additionally, the techniques may be used for stimulation ofnerve ganglia including, e.g., one or more ganglia of a nerve plexus. Asan additional example, the techniques disclosed herein may be used inthe treatment of vascular baroreceptors including, e.g., carotidbaroreceptors. In the example shown in FIG. 1A, electrodes of lead 28are position to deliver electrical stimulation to target tissue site 40proximate a vagus nerve of patient 12. The vagus nerve is primarilyreferred to herein as an example target nerve for neurostimulationtherapy.

In some examples, delivery of electrical stimulation to a nerve tissuesite may provide cardiac benefits to patient 12. For example, deliveryof electrical stimulation to a peripheral nerve tissue site by IMD 16may help treat heart failure. In addition, delivery of electricalstimulation to a nerve of patient 12 may help reduce or eliminatecardiovascular conditions such as bradycardia, tachycardia, unhealthycardiac contractions, ischemia, inefficient heart pumping, inefficientcollateral circulation of heart 14 or cardiac muscle trauma. Inaddition, delivery of electrical stimulation to a nerve may complementantitachycardia pacing or provide back-up therapy to cardiac therapydelivered by IMD 16. In some examples, IMD 16 may deliver electricalstimulation therapy to a nerve of patient 12 via a lead implanted withinvasculature (e.g., a blood vessel) of patient 12. In other examples,stimulation may be delivered by IMD 16 via a lead located inextravascular tissue, e.g., when lead 28 is not implanted withinvasculature, such as within a vein or artery. Additional examplesinclude transvascular placement of a lead from within a blood vessel ofpatient 12 adjacent the target tissue site, through the wall of theblood vessel, and into an extravascular space, where the target nervetissue may be located.

In the example shown in FIG. 1A, the neurostimulation therapy module ofIMD 16 delivers electrical stimulation therapy to a nerve of patient 12via a lead implanted within vasculature (e.g., a blood vessel) ofpatient 12. In particular, lead 28 is implanted such that electrodes oflead 28 are positioned within jugular vein 46 proximate the vagus nerve(not shown). Stimulation of a parasympathetic nerve of patient 12 mayhelp slow intrinsic rhythms of heart 14, which may complementantitachyarrhythmia therapy (e.g., antitachycardia pacing, cardioversionor defibrillation) delivered by IMD 16. In this way, neurostimulationtherapy may help control a heart rate of patient 12 or otherwise controlcardiac function.

In other examples, electrodes of lead 28 may be positioned to deliverelectrical stimulation to any other suitable nerve (e.g., a peripheralnerve) or nerve tissue in patient 12. In some examples, theneurostimulation module of IMD 16 may deliver electrical stimulation toother sympathetic or parasympathetic nerves, baroreceptors, hypoglossalnerve, carotid sinus, or a cardiac branch of the vagal trunk of patient12 in order to facilitate or compliment the delivery of therapy by thecardiac therapy module of IMD 16.

In FIG. 1A, leads 18, 20, and 22 extend into the heart 14 of patient 12to sense electrical activity (electrical cardiac signals) of heart 14and/or deliver electrical stimulation (cardiac therapy) to heart 14. Inparticular, right ventricular (RV) lead 18 extends through one or moreveins (not shown), superior vena cava (not shown), and right atrium 30,and into right ventricle 32. Left ventricular (LV) coronary sinus lead20 extends through one or more veins, the vena cava, right atrium 30,and into coronary sinus 34 to a region adjacent to the free wall of leftventricle 36 of heart 14. Right atrial (RA) lead 22 extends through oneor more veins and the vena cava, and into right atrium 30 of heart 14.In other examples, IMD 16 is additionally or alternatively coupled toextravascular, e.g., epicardial or subcutaneous electrodes, via leadsfor cardiac sensing and/or stimulation.

The cardiac therapy module may sense electrical signals attendant to thedepolarization and repolarization of heart 14 via electrodes (not shownin FIG. 1A) coupled to at least one of the leads 18, 20, 22. Theseelectrical signals within heart 14 may also be referred to as cardiacsignals or electrical cardiac signals. In some examples, the cardiactherapy module provides pacing pulses to heart 14 based on theelectrical cardiac signals sensed within heart 14. The configurations ofelectrodes used by the cardiac therapy module for sensing and pacing maybe unipolar or bipolar. The cardiac therapy module may also providedefibrillation therapy and/or cardioversion therapy via electrodeslocated on at least one of the leads 18, 20, 22 and one or moreelectrodes on housing 44 of IMD 16. IMD 16 may detect arrhythmia ofheart 14, such as fibrillation of ventricles 32 and 36, and deliverdefibrillation therapy to heart 14 in the form of electrical pulses viaone or more of leads 18, 20, and 22. In some examples, the cardiactherapy module may be programmed to deliver a progression of therapies,e.g., pulses with increasing energy levels, until a fibrillation ofheart 14 is stopped. IMD 16 detects fibrillation employing one or morefibrillation detection techniques known in the art.

The neurostimulation therapy module of IMD 16 may provide a programmablestimulation signal (e.g., in the form of electrical pulses or acontinuous signal) that is delivered to target stimulation site 40 byimplantable medical lead 28, and more particularly, via one or morestimulation electrodes carried by lead 28. Proximal end 28A of lead 28may be both electrically and mechanically coupled to connector 42 of IMD16 either directly or indirectly (e.g., via a lead extension). Inparticular, conductors disposed in the lead body of lead 28 mayelectrically connect stimulation electrodes (and sense electrodes, ifpresent) of lead 28 to IMD 16. In some examples, the neurostimulationtherapy module of IMD 16 may be electrically coupled to more than onelead directly or indirectly (e.g., via a lead extension).

In the example of FIG. 1A, one or more electrodes of lead 28 areintravascularly implanted in patient 12 proximate to target tissuestimulation site 40, e.g., proximate to a vagus nerve (not shown). Inparticular, one or more neurostimulation electrodes of lead 28 areimplanted within jugular vein 46. Generally speaking, implanting lead 28near the vagus nerve of patient 12 may be useful for deliveringneurostimulation therapy to the vagus nerve without requiring lead 28 tobe subcutaneously implanted in patient 12. Implanting lead 28intravascularly within jugular vein 46 may thereby be useful forreducing trauma to patient 12, e.g., because lead 28 is not tunneledthrough subcutaneous tissue from IMD 16 to target site 40. As describedin greater detail with reference to FIGS. 4-22, in other examplesaccording to this disclosure, lead 28 may be extravascularly ortransvascularly placed proximate target tissue stimulation site 40,e.g., proximate a vagus nerve of patient 12.

The distal portion of lead 28 may include one or more electrodes (notshown) for delivering neurostimulation to target stimulation site 40.Various electrode configurations of lead 28 are described in furtherdetail with respect to FIGS. 2 and 3. In some examples, lead 28 may alsocarry sense electrodes (not shown) to permit IMD 16 to sense electricalsignals, such as electrical cardiac signals or electrical nerve signalsfrom the vagus nerve or other nerve tissue at which therapy is directed.Lead 28 may also carry one or more sensors including, e.g., senseelectrodes, pressure sensors, ultrasound sensors, motion sensors,acoustic sensors (heart rate), optical sensors, blood oxygen sensors,posture state sensors, respiration sensors, venous biomarker sensors,temperature sensors or other devices that may detect physiologicalsignals of patient 12 indicative of the efficacy of neurostimulationtherapy delivered to the patient by stimulation electrodes.

In some examples, IMD 16 may deliver an electrical stimulation signalvia one or more of the electrodes of lead 28, and analyze aphysiological signal to detect a response to the stimulation signal. Inone such example, IMD 16 analyzes an electrical nerve signal to detect aresponse to the stimulation signal. The characteristic of the electricalnerve signal that indicates the desired response to the delivery of theelectrical stimulation signal by the neurostimulation therapy module ofIMD 16 may be, for example, an amplitude or frequency of the electricalsignal. The target characteristic of the electrical nerve signal may bedetermined by a clinician at any suitable time when lead 28 is known tobe in the desired location within patient 12, e.g., immediately afterlead 28 is implanted within patient 12.

The electrical nerve signal may be an electrical signal generated by anerve, such as the target nerve for the neurostimulation therapy or abranch thereof, in response to an electrical stimulation signaldelivered by the electrodes of lead 28. The response to the electricalstimulation signal may indicate, for example, whether theneurostimulation signal captured the nerve, and, therefore, is within adesired distance of the nerve. In the example shown in FIG. 1A, thetarget nerve is a vagus nerve, however, other types of nerves arecontemplated for the neurostimulation therapy. The electrical nervesignal may be sensed between two or more electrodes of lead 28. IMD 16may analyze the electrical nerve signal for a response, for example, bymeasuring an amplitude of the electrical nerve signal and comparing thedetermined value to a threshold value. In this case, the electricalnerve signal may have a baseline amplitude value and a response to thestimulation signal may be characterized by a spike in amplitude. Thenerve response may be characterized by an amplitude or othercharacteristics of a sensed electrical signal.

In the context of lead placement techniques disclosed herein, sensedphysiological signals may be used to determine the efficacy ofneurostimulation delivered by electrodes on lead 28 to target nervetissue. In some examples, lead 28 may be intra, extra, ortransvascularly placed proximate the nerve tissue and electrodes on lead28 may deliver test stimulation pulses to the nerve tissue in order totest the placement of lead 28 within patient 12 relative to the nervetissue. Various physiological signals may be observed to measure theefficacy of the test stimulation, and thereby the need to repositionlead 28 relative the target nerve tissue. In some examples, testtreatment efficacy may be indicated by, e.g., ECG, heart rate, bloodpressure, blood flow, blood oxygen content, blood biomarker content,cardiac output, and/or breathing, of patient 12. Additionally, T-wavemorphology, heart rate variability, contractility, and atrioventricular(AV) intervals may be observed as an indication of test treatmentefficacy. These and other physiological signals may be detected in avariety of ways including sensing the signals using sense electrodes,pressure sensors, ultrasound sensors, motion sensors or other devices.In other examples, physiological reactions of patient 12 may be observedor measured by, e.g., a clinician.

In the case one or more sensors are employed to detect physiologicalsignals of patient 12, such devices may be arranged in a variety oflocations depending on device configuration and the particular signalbeing detected. For example, the efficacy of electrical stimulation of avagus nerve may be measured by an accelerometer arranged in the neck ofpatient 12 that determines if stimulation of neck muscles or the phrenicnerve is occurring with or instead of stimulation of a vagus nerve. Inanother example, a pressure sensor arranged coincident with or connectedto lead 28 may measure blood pressure by detecting the pressure within avessel in which lead 28 is placed. A pressure sensor, or other type ofphysiological feedback sensor, may also, in some examples, be connectedto a delivery catheter configured to place lead 28 within patient 12. Instill another example, a cardiac therapy module included in IMD 16 mayemploy one or more electrodes arranged on or within heart 14 of patient12 to, e.g., to monitor electrical activity of heart 14 via anelectrogram (EGM) or electrocardiogram (ECG) signal. In other examples,venous biomarker sensors configured to sense, e.g., inflammation markersor catecholamines may be used to measure the effect of the stimulationand provide feedback to IMD 16.

The extra, intra, and transvascular lead placement techniques describedherein are applicable for implantation of a variety of implantabletherapy systems including, e.g., system 10 of FIG. 1A, as well assystems that do not deliver cardiac stimulation and/or provide cardiacsensing, or, as with the example of FIG. 1B, deliver cardiac therapyusing a device that is separate from and in addition to an implantableneurostimulator.

As illustrated in FIG. 1A, system 10 may include a programmer 24. IMD 16may transmit information to and receive information from programmer 24related to the operation of IMD 16 and/or the delivery of therapy by IMD16 to patient 12. Upon receiving the information, programmer 24 mayupload the received information to a remote server, from which aclinician may access the data (such as a remote server of the CareLinkNetwork available from Medtronic, Inc. of Minneapolis, Minn.). Aclinician may also access the information directly by interacting withprogrammer 24. Furthermore, the clinician may program various aspects ofthe operation of IMD 16 remotely by accessing a remote server thatcommunicates with IMD 16 via a network and programmer 24, or locallyprogram IMD 16 by physically interacting with programmer. In someexamples, the clinician may interact with programmer 24 to, e.g.,program select values for operational parameters of IMD 16.

In some examples, programmer 24 may be a handheld computing device or acomputer workstation. The user may use programmer 24 to program aspectsof the neurostimulation module. The therapy parameters for theneurostimulation module of IMD 16 may include an electrode combinationfor delivering neurostimulation signals, as well as an amplitude, whichmay be a current or voltage amplitude, and, if the neurostimulationmodule delivers electrical pulses, a pulse width, and a pulse rate forstimulation signals to be delivered to patient 12. The electrodecombination may include a selected subset of one or more electrodeslocated on implantable lead 28 coupled to IMD 16 and/or a housing of IMD16. The electrode combination may also refer to the polarities of theelectrodes in the selected subset. By selecting particular electrodecombinations, a clinician may target particular anatomic structureswithin patient 12. In addition, by selecting values for amplitude, pulsewidth, and pulse rate, the physician can attempt to generate anefficacious therapy for patient 12 that is delivered via the selectedelectrode subset.

As another example, programmer 24 may be used by a user, e.g., aclinician while a medical lead is placed within patient in accordancewith this disclosure to retrieve or view sensor feedback during theimplantation of the lead. In one example, a physician uses programmer 24to retrieve and/or view physiological signals sensed by one or moresensors in response to test electrical stimulation pulses delivered topatient 12 during the placement of lead 12 adjacent a vagus nerve. Inthis manner, the physician employs programmer 24 to determine theefficacy of the test stimulation delivered by lead 28, and thereby theposition of lead 28 relative to the vagus nerve. In another example, thephysician may also use programmer 24 to view an imaging field producedby an IVUS imaging system connected to a delivery catheter used to placelead 28, and electrodes connected thereto intra or transvascularlywithin patient 12. In this manner, the physician may employ programmer24 to view, in real time, the placement of lead 28 within patient 12relative to target nerve tissue and a blood vessel in which or throughwhich the lead is placed.

Programmer 24 may communicate with IMD 16 via wireless communicationusing any techniques known in the art. Examples of communicationtechniques may include, for example, low frequency or radiofrequency(RF) telemetry, but other techniques are also contemplated. In someexamples, programmer 24 may include a programming head that may beplaced proximate to the patient's body near the IMD 16 implant site inorder to improve the quality or security of communication between IMD 16and programmer 24.

FIG. 1B is a conceptual diagram illustrating another example therapysystem 11 that includes separate implantable cardiac device (ICD) 17 andimplantable electrical stimulator 26. ICD 17 is connected to leads 18,20, and 22, and programmer 24, while electrical stimulator 26 is coupledto lead 28 and may be communicatively connected to both ICD 17 andprogrammer 24. ICD 17 may be, for example, a device that providescardiac rhythm management therapy to heart 14, and may include, forexample, an implantable pacemaker, cardioverter, and/or defibrillator,as described above with reference to IMD 16.

In some examples, ICD 17 may, in addition to or instead of deliveringcardiac rhythm management therapy to heart 14, sense electrical cardiacsignals of heart 14 and/or other physiological parameters of patient 12(e.g., blood oxygen saturation, blood pressure, temperature, heart rate,respiratory rate, and the like), and store the electrical cardiacsignals and/or other physiological parameters of patient 12 for lateranalysis by a clinician. In such examples, ICD 17 may be referred to asa patient monitoring device. Examples of patient monitoring devicesinclude, but are not limited to, the Reveal Plus Insertable LoopRecorder, which is available from Medtronic, Inc. of Minneapolis, Minn.For ease of description, ICD 17 will be referred to herein as a cardiacrhythm management therapy delivery device.

Therapy system 11 also includes implantable electrical stimulator 26,which is coupled to lead 28. Electrical stimulator 26 may also bereferred to as an implantable neurostimulator (“INS”) 26. INS 26 may beany suitable implantable medical device (IMD) that includes a signalgenerator that generates electrical stimulation signals that may bedelivered via one or more electrodes on lead 28 to a nerve tissue siteof patient 12, e.g., tissue proximate a vagus nerve.

In the example shown in FIG. 1B, electrodes of lead 28 are positionedoutside the vasculature of patient 12 to deliver electrical stimulationto a vagus nerve (not shown) of patient 12. As described above, in otherexamples, stimulation may be delivered to a nerve tissue site viaelectrodes of an intravascular lead that is implanted withinvasculature. In still other examples, stimulation may be delivered to anerve tissue site within patient 12 via electrodes of a transvascularlead that is guided proximate the target tissue site intravascularly,i.e., through a vein, artery, or other blood vessel and then pierces awall of the vessel to be arranged adjacent the target tissue outside ofthe blood vessel.

In the example shown in FIG. 1B, the components of ICD 17 and INS 26 areenclosed in separate housings, such that ICD 17 and INS 26 arephysically separate devices. In contrast to the example of FIG. 1A inwhich the functionality of ICD 17 and INS 26 are be performed by IMD 16that includes both a cardiac therapy module and an electricalstimulation therapy module. In applications in which cardiac andneurostimulation therapy operate cooperatively or sensing feedback isprovided from heart 14 or a nerve tissue site within patient 12, ICD 17and INS 26 of FIG. 1B may communicate with one another via one or morewireless communication techniques instead of being directly linkedwithin the same device housing as in IMD 16 of therapy system 10 shownin FIG. 1A. For example, INS 26 may include one or more sensors thatanalyze an electrical nerve signal to detect a response to thestimulation signal delivered by ICD 17 and/or INS 26 to patient 12. ICD17 and INS 26 may communicate wirelessly using, e.g., low frequency orradiofrequency (RF) telemetry.

FIG. 2 is a functional block diagram of an example configuration of IMD16 of FIG. 1A, which includes processor 100, memory 102, cardiac therapymodule 104, neurostimulation therapy module 106, telemetry module 108,and power source 110. Cardiac therapy module 104 includes signalgenerator 112 and sensing module 114. Neurostimulation therapy module106 includes signal generator 116 and sensing module 118. The componentsof IMD 16 shown in FIG. 2 may be substantially enclosed within a common,hermetically sealed outer housing 44 of IMD 16. In other examplesincluding the example shown in FIG. 1B, components for carrying out thefunctions of cardiac therapy module 104 and neurostimulation therapymodule 106 may be arranged in separate communicatively connecteddevices. Although cardiac therapy module 104 and neurostimulationtherapy module 106 are illustrated as separate modules in FIG. 4, insome examples, cardiac therapy module 104 and neurostimulation module106 and their respective components may share circuitry. For example,signal generators 112 and 116 may share common circuitry, e.g., astimulation engine, charging circuitry, capacitors, and the like.Additionally, in some examples in which cardiac therapy module 104 andneurostimulation module 106 deliver stimulation in alternation, cardiactherapy module 104 and neurostimulation module 106 may share some or allstimulation generation circuitry. Similarly, in some examples, sensingmodules 114 and 118 may also share common circuitry, such as ananalog-to-digital converter and the like.

Memory 102 includes computer-readable instructions that, when executedby processor 100, cause IMD 16 and processor 100 to perform variousfunctions attributed to IMD 16 and processor 100 herein. In FIG. 2,memory 102 includes cardiac programs 122 that cardiac therapy module 104uses for generating cardiac rhythm therapy for delivery to heart 14, andneurostimulation programs 124 that neurostimulation module 106 uses forgenerating neurostimulation therapy for delivery to target tissue site40. Memory 102 may include any volatile, non-volatile, magnetic,optical, or electrical media, such as a random access memory (RAM),read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasableprogrammable ROM (EEPROM), flash memory, or any other digital media.

Processor 100 may include any one or more of a microprocessor, acontroller, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), orequivalent discrete or integrated logic circuitry. In some examples,processor 100 may include multiple components, such as any combinationof one or more microprocessors, one or more controllers, one or moreDSPs, one or more ASICs, or one or more FPGAs, as well as other discreteor integrated logic circuitry. The functions attributed to processor 100herein may be embodied as software, firmware, hardware or anycombination thereof. Processor 100 may control cardiac therapy module104 to deliver stimulation therapy according to a selected one or moreof cardiac programs 122 stored in memory 102. In addition, processor 100may control neurostimulation module 106 to delivering stimulationtherapy according to a selected one or more of neurostimulation programs124 stored in memory 102. Specifically, processor 100 may controlcardiac therapy module 104 and/or neurostimulation module 106 to deliverelectrical signals via electrode combinations with amplitudes,frequency, electrode polarities, and, in the case of stimulation pulses,pulse widths specified by the selected one or more cardiac andneurostimulation therapy programs 122, 124, respectively.

In the example shown in FIG. 2, cardiac therapy module 104 iselectrically connected to electrodes 50, 52, 54, 56, 58, 60, 72, 74, and76 of leads 18, 20, and 22 and housing electrode 68, andneurostimulation module 106 is electrically connected to electrodes80-83 of lead 28 and housing electrode 68. In other examples, cardiactherapy module 104 and neurostimulation module 106 may be coupled to anysuitable number of electrodes, which may comprise a greater number ofelectrodes or a fewer number of electrodes than that shown in theexample of FIG. 2.

Cardiac therapy module 104 is configured to generate and deliver cardiacrhythm therapy to heart 14. For example, signal generator 112 of cardiactherapy module 104 may generate and deliver cardioversion ordefibrillation shocks and/or pacing pulses to heart 14 via a selectedcombination of electrodes 50, 52, 54, 56, 58, 60, 72, 74, and 76 andhousing electrode 68. Signal generator 112 of cardiac therapy module 104is electrically coupled to electrodes 50, 52, 54, 56, 58, 60, 72, 74,and 76, e.g., via conductors of the respective lead 18, 20, 22, or, inthe case of housing electrode 68, via an electrical conductor disposedwithin housing 44 of IMD 16.

Sensing module 114 monitors signals from at least one of electrodes 50,52, 54, 56, 58, 60, 72, 74, and 76 in order to monitor electricalactivity of heart 14, e.g., via an EGM or ECG signal. Sensing module 114may also include a switching module (not shown in FIG. 4) to select aparticular subset of available electrodes to sense heart activity. Inthis manner, sensing module 114 may detect R-waves, P-waves, or othercardiac electrical activity, and provide indications of their occurrenceto processor 100. In some examples, processor may analyze a digitizedthe EGM or ECG to detect these or other morphological features of theEGM or ECG, to determine heart rates or intervals (e.g., R-R intervals)or sizes of features such as T-waves or QRS complexes, or provide anyother known cardiac sensing and monitoring functionality.

Neurostimulation module 106 is configured to generate and deliverelectrical stimulation therapy to a target site within patient 12proximate nerve tissue, e.g., in order to modulate an autonomic nervoussystem or vascular tone. Example stimulation sites for neurostimulationmodule 106 include, but are not limited to, tissue proximate a vagusnerve or braches of a vagus nerve of patient 12. For example, signalgenerator 116 may generate stimulation signals that are delivered to atissue site proximate a vagus nerve via a selected combination ofelectrodes 80-83 of lead 28 and/or housing electrode 68. The stimulationsignals may be pulses as primarily described herein, or continuous timesignals, such as sine waves.

Signal generator 116 may be a single or multi-channel signal generator.In particular, signal generator 116 may be capable of delivering, asingle stimulation pulse, multiple stimulation pulses, or a continuoussignal at a given time via a single electrode combination or multiplestimulation pulses at a given time via multiple electrode combinations.In some examples, however, neurostimulation therapy module 106 may beconfigured to deliver multiple channels on a time-interleaved basis. Inthis case, neurostimulation therapy module 106 may include a switchingmodule (not shown) that serves to time division multiplex the output ofthe signal generator across different electrode combinations atdifferent times to deliver multiple programs or channels of stimulationenergy to patient 12.

Sensing module 118 of neurostimulation module 106 monitors signals fromat least one of electrodes 80-83 of lead 28 and housing electrode 68 inorder to monitor electrical activity of the target nerve tissue, e.g.nerve signals of a vagus nerve. For example, the amount of afferent andefferent signals of nerve fibers can be monitored. In one such example,the nerve signals of the left vagus nerve of patient 12 can be comparedto the right vagus nerve and therapy may be delivered byneurostimulation module 106 and/or cardiac therapy module 104 ascommanded by processor 100 based at least in part upon this comparisonof sensed nerve tissue traffic. Conversely, in the context of leadplacement techniques described herein, therapy may be delivered to avagus nerve (e.g. left or right, or both) by one or more of electrodes80-83 and sensing module 118 of neurostimulation module 106 and/orsensing module 114 of cardiac therapy module 104 as commanded byprocessor 100 may monitor afferent and efferent signals of vagal nervefibers to measure the efficacy of the therapy.

Telemetry module 108 includes any suitable hardware, firmware, softwareor any combination thereof for communicating with another device, suchas programmer 24 (FIG. 1). Under the control of processor 100, telemetrymodule 108 may receive downlink telemetry from and send uplink telemetryto programmer 24 with the aid of an antenna, which may be internaland/or external. Processor 100 may provide the data to be uplinked toprogrammer 24 and the control signals for the telemetry circuit withintelemetry module 108, e.g., via an address/data bus. In some examples,telemetry module 108 may provide received data to processor 100 via amultiplexer.

The various components of IMD 16 are coupled to power source 100, whichmay include a rechargeable or non-rechargeable battery or asupercapacitor. A non-rechargeable battery may be selected to last forseveral years, while a rechargeable battery may be inductively chargedfrom an external device, e.g., on a daily or weekly basis. Power source100 may also include an external or a subcutaneously implanted RFtransmitter that is configured to deliver power via radio frequencypulses to a receiver arranged with IMD 16 or one of the leads and/orelectrodes of cardiac therapy module 104 and neurostimulation therapymodule 106. In other examples, some part of IMD 16, or one of the leadsor electrodes may be composed of a piezoelectric material that cangenerate current when excited mechanically by ultra sound wavestransmitted from an external or implanted source.

In some examples, data generated by sensing module 114 or sensing module118 and stored in memory 102 may be uploaded to a remote server, fromwhich a clinician or another user may access the data to determinewhether a potential sensing integrity issue exists. An example of aremote server includes the CareLink Network, available from Medtronic,Inc. of Minneapolis, Minn. An example system may include an externaldevice, such as a server, and one or more computing devices that arecoupled to IMD 16 and programmer 24 via a network.

In addition to the examples of FIGS. 1A, 1B, and 2 including cardiactherapy and neurostimulation therapy implemented in a single or separatedevices, examples according to this disclosure also include a standaloneINS device implanted within patient 12 and configured to function in amanner consistent with the description of neurostimulation therapymodule 106 of IMD 16 or INS 26 shown in FIGS. 1A and 2, and 1Brespectively.

FIG. 3 is block diagram of example programmer 24 of FIGS. 1A and 1B. Asshown in FIG. 3, programmer 24 includes processor 130, memory 132, userinterface 134, telemetry module 136, and power source 138. Programmer 24may be a dedicated hardware device with dedicated software forprogramming one or more of IMD 16, ICD 17, or INS 26. Alternatively,programmer 24 may be an off-the-shelf computing device running anapplication that enables programmer 24 to program one or more of IMD 16,ICD 17, or INS 26. For convenience and clarity, the description of FIG.3 will be made with reference to the operation of programmer 24 with IMD16. However, the components and functions of programmer 24 describedherein are equally applicable to use with ICD 17, INS 26 or any otherimplantable medical device that may benefit from the functions providedby an external programming device such as programmer 24.

A user may use programmer 24 to select therapy programs (e.g., sets ofstimulation parameters), generate new therapy programs, modify therapyprograms through individual or global adjustments or transmit the newprograms to IMD 16 (FIG. 1A). The therapy programs may be for either orboth cardiac therapy module 104 and neurostimulation module 106 (FIG.2). A clinician, e.g., may interact with programmer 24 via userinterface 134, which may include a display to present a graphical userinterface to a user, and a keypad or another mechanism for receivinginput from a user.

Processor 130 can take the form of one or more microprocessors, DSPs,ASICs, FPGAs, programmable logic circuitry, or the like, and thefunctions attributed to processor 130 herein may be embodied ashardware, firmware, software or any combination thereof. Memory 132 maystore instructions that cause processor 130 to provide the functionalityascribed to programmer 24 herein, and information used by processor 130to provide the functionality ascribed to programmer 24 herein. Memory132 may include any fixed or removable magnetic, optical, or electricalmedia, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM,or the like. Memory 132 may also include a removable memory portion thatmay be used to provide memory updates or increases in memory capacities.A removable memory may also allow patient data to be easily transferredto another computing device, or to be removed before programmer 24 isused to program therapy for another patient. Memory 132 may also storeinformation that controls therapy delivery by IMD 16, such asstimulation parameter values.

Programmer 24 may communicate wirelessly with IMD 16, such as using RFcommunication or proximal inductive interaction. This wirelesscommunication is possible through the use of telemetry module 136, whichmay be coupled to an internal antenna or an external antenna. Anexternal antenna that is coupled to programmer 24 may correspond to theprogramming head that may be placed proximate to the patient's body nearthe IMD 16 implant site, as described above with reference to FIG. 1A.Telemetry module 136 may be similar to telemetry module 108 of IMD 16(FIG. 2).

Telemetry module 136 may also be configured to communicate with anothercomputing device via wireless communication techniques, or directcommunication through a wired connection. Examples of local wirelesscommunication techniques that may be employed to facilitatecommunication between programmer 24 and another computing device includeRF communication according to the 802.11 or Bluetooth specificationsets, infrared communication, e.g., according to the IrDA standard, orother standard or proprietary telemetry protocols. In this manner, otherexternal devices may be capable of communicating with programmer 24without needing to establish a secure wireless connection.

Power source 138 delivers operating power to the components ofprogrammer 24. Power source 138 may include a battery and a powergeneration circuit to produce the operating power. In some examples, thebattery may be rechargeable to allow extended operation of programmer24.

FIGS. 4 and 5 are schematic illustrations depicting relevant anatomy forlead placement techniques described herein. FIG. 4 illustrates vagusnerve 150 including many branches, such as pharyngeal and laryngealbranches 152, cardiac branches 154, as well as the gastric andpancreaticoduodenal branches (not specifically labeled in FIG. 4). Theillustration of FIG. 5 is a cross section through the neck of patient 12that shows carotid sheath 156 in which is contained internal jugularvein 158, carotid artery 160, and left and right vagus nerves 150L and150R respectively. Vagus nerve 150 originates in the brainstem, runs inthe neck through carotid sheath 156 with jugular vein 158 and commoncarotid artery 160, and then adjacent to the esophagus to the thoracicand abdominal viscera. Vagus nerve 150 provides the primaryparasympathetic nerve to the thoracic and most of the abdominal organs.For example, vagus nerve 150 provides parasympathetic innervation to theheart, and stimulation of the nerve has been demonstrated to drive theparasympathetic nervous system and thereby overcome an acceleratedsympathetic tone, which may be exhibited by patients suffering fromvarious tachycardia conditions, as well as heart failure. In one suchtachycardia application, the efferent fibers of the vagus nerve, such asone or more superior and/or inferior cardiac branches may beelectrically stimulated to manage the accelerated arrhythmia. Vagalnerve stimulation may also have afferent effects that result in nervereflex changes that affect heart rate. In addition to heartinnervations, vagus nerve 150 is responsible for such varied tasks asgastrointestinal peristalsis, sweating, as well as muscle movementsrelated to speech. Electrical stimulation of vagus nerve 150 may beuseful in treating, not only heart failure and arrhythmia conditions,but also various other conditions including, e.g., depression, epilepsy,and various gastrointestinal conditions. To determine the need forand/or response to nerve tissue stimulation according to methods andsystems disclosed herein, ECG, heart rate, blood pressure, blood flow,cardiac output, and/or breathing, for instance, of patient 12 can besensed. Such patient feedback information can be gleaned from, e.g.,clinician observation, as well as employing one of implantable cardiacdevice (ICD) 17 shown in FIG. 1B or cardiac therapy module 104 shown inFIG. 2. Again, although the techniques disclosed herein are describedgenerally in the context of stimulation of one of the vagus nerves onthe vagal nerve trunk in the neck of a human patient, the methods andsystems disclosed are also applicable to stimulation and treatment ofother nerve tissues that are located in diverse locations including,e.g., baroreceptors, hypoglossal nerves, and nerve plexus and ganglia.

In addition to various biological structures of patient 12, FIG. 5 showsintra and extravascularly placed leads 29′ and 29″ respectively. Medicallead 29 is used for purposes of describing placement techniquesaccording to this disclosure. In general, lead 29 may correspond to lead28 shown in FIGS. 1A and 1B above. Intravascular lead 29′ is arrangedwithin internal jugular vein 158, while extravascular lead 29″ isarranged within carotid sheath 156, adjacent vagus nerve 150. Inaddition to intra and extravascular leads 29′ and 29″ shown in FIG. 5,examples according to this disclosure include transvascular placement oflead 29 such that the lead passes from within a blood vessel of patient12 through a wall of the vessel to terminate adjacent a target nervetissue stimulation site. For example, lead 29 may be guided proximate atarget site intravascularly through internal jugular vein 158 and thenpierce a wall of jugular vein 158 to be arranged adjacent vagus nerve150. Although the examples disclosed herein are generally described inthe context of stimulating vagal nerves in the neck of patient 12, lead29 and electrodes attached thereto may also be arranged for vagal nervestimulation in, e.g., the thorax, and/or adjacent to the esophagus.

Extravascular lead placement techniques according to this disclosureprovide placement of leads for nerve tissue stimulation and/or nervesignal sensing using implantation procedures with reduced invasivenessand without the need to anchor the leads at or very near their distalend. In general, the disclosed techniques include placing a portion of amedical lead having an electrode in an extravascular space within asheath of tissue within a patient, and adjacent nerve tissue that isalso within the sheath of tissue. The lead is anchored offset from theelectrode at least partially outside of the sheath.

FIGS. 6-8 illustrate examples of extravascular lead placement techniquesin the context of vagal nerve stimulation in a human patient. FIG. 6 isa schematic illustration depicting lead 29 extravascularly placedadjacent vagus nerve 150 within carotid sheath 156 in patient 12. Afteror during placement, lead 29 may be connected to IMD 16 or INS 26similar to lead 28 shown in FIGS. 1A and 1B respectively. FIG. 7 is aflow chart illustrating an example method of placing lead 29 inaccordance with the example of FIG. 6. The example method of FIG. 7generally includes placing a portion of a medical lead having anelectrode electrically connected thereto in an extravascular spaceadjacent nerve tissue within a sheath of tissue within a patient (180),anchoring the lead offset from the electrode outside of the sheath,(182), and stimulating the nerve tissue (184). One example of the methodillustrated in FIG. 7 will be described in the context of the examplelead placement shown in FIG. 6.

The arrangement shown in FIG. 6 includes lead 29, electrodes 170, andanchor 172. Electrodes 170 are connected to and arranged toward a distalend of lead 29. The example of FIG. 6 also includes biasing member 176and deployable lobe member 178 connected to lead 29 to bias and/orstabilize lead 29 and electrodes 170 toward vagus nerve 150. Althoughthe example of FIG. 6 shows four electrodes 170, other examples mayinclude fewer or more electrodes connected to lead 29 and, in somecases, other leads in addition to lead 29. In some examples, electrodes170 may include multiple types including, e.g., electrode pads on apaddle lead, circular (e.g., ring) electrodes surrounding the body ofleads 16, conformable electrodes, segmented electrodes, or any othertype of electrodes capable of forming unipolar, bipolar or multipolarelectrode configurations for delivering nerve tissue stimulation therapyto patient 12. In some examples including ring electrodes, electrodes170 may be arranged on lead 29 with part of the rings electricallyinsulated to limit the spread of the stimulating field so that only aportion of the electrodes and electrical stimulation may be directed atvagus nerve 150.

The distal end of lead 29 to which electrodes 170 are attached isarranged within carotid sheath 156, adjacent vagus nerve 150. Biasingmember 176 and deployable lobe member 178 are arranged at the distal endof lead 29 and bias lead 29 toward vagus nerve 150 by exerting a forceon surrounding tissue including, e.g., internal jugular vein 158. Aproximate end of lead 29 (not shown in FIG. 6) may be connected to IMD16 (see FIG. 1A). Anchor 172 is connected to lead 29 offset from thedistal end of lead 29 outside of carotid sheath 156. Anchor 172 may beany suitable fixation element that stabilizes the placement of lead 29and electrodes 170 within sheath 156 adjacent vagus nerve 150. Forexample, anchor 172 may be one of a variety of sutureless fixationelements connected to lead 29 that are configured to engage tissue ofpatient 12 outside of carotid sheath 156. In one example, one or moretines or barbs may protrude from lead 29 to pierce and thereby attachlead 29 to tissue of patient 12 outside of sheath 156. In addition to orinstead of sutureless anchors, anchor 172 may include various fixationelements that engage lead 29 and are configured to be sutured by aclinician to the tissue of patient 12 outside of carotid sheath 156.Additionally, in some examples, anchor 172 may include a sleeveconfigured to receive lead 29 therethrough and tabs protruding from thesleeve that may passively engage or be sutured to tissue of patient 12.In some examples, such sleeve anchors may be used to seal a tissueaccess site, such as incision 174 in carotid sheath 156. Anchor 172 isoffset from the most proximal of electrodes 172 by a distance D. In someexamples, the offset distance D of anchor 172 from the most proximal ofelectrodes 172 is in the range from and including approximately 1 cm toand including approximately 15 cm. In other examples, the offsetdistance D may be in the range from and including approximately 1 cm toand including approximately 2 cm.

In practice, a variety of techniques may be employed to extravascularlyplace lead 29 within carotid sheath 156 adjacent vagus nerve 150. In theexample of FIG. 6, the portion of carotid sheath 156 and surroundingtissue of patient 12 shown may be exposed by an incision in the neck ofthe patient. However, because lead 29 is not anchored at the distal endthat is arranged within carotid sheath 156, all of or even a portion ofvagus nerve 150 need not be dissected from sheath 156. Instead, lead 29may be guided through a relatively small incision 174 in carotid sheath156 to place the distal end of lead 29 including electrodes 170 adjacentvagus nerve 150. Lead 29 may be placed through incision 174 withincarotid sheath 156 using a variety of introducer elements including,e.g., a catheter and/or a guide wire to stabilize and guide theplacement of lead 29 adjacent vagus nerve 150. Lead 29 may be stiffenedwithin carotid sheath 156 by, e.g., the guide wire or a stylus.Additionally, the distal end of lead 29 including electrodes 170 may bebiased toward vagus nerve 150 using biasing member 176. Biasing member176 may be, e.g. an inflatable or otherwise expandable structureincluding, e.g. a stent-like member or a balloon as schematicallyillustrated in FIG. 6. In other examples, biasing member 176 may bestatic, e.g. protruding tines, or retractable and/or deployable, e.g.one or more elongated splines or lobes that deflect away from lead 29when placed under tension. For example, in addition to biasing member176, the example of FIG. 6 includes deployable lobe member 178 includinga plurality of deployable lobes that protrude from and arecircumferentially distributed about lead 29.

An example of deployable lobe member 178 may be the Attain® StarFix™fixation element included in the over-the-wire lead Model 4195 developedand sold by Medtronic, Inc. of Minneapolis, Minn. The design of thisfixation element allows clinicians to place and stabilize elongatedmedical electrical leads within patients. The StarFix™ element generallyincludes a number of deployable lobes that are formed lengthwise on aninsulating sheath that surrounds the medical lead by pairs of elongated,parallel cuts or slits. The deployable lobes are formed by the materialbetween the elongated, substantially parallel slits. The spacing betweenthe slits generally defines the width of the deployable lobe formedtherebetween. Accordingly, the rigidity of each lobe may be increased ordecreased by increasing or decreasing the distance between the parallelslits that define the lobe. The rigidity of the lobes may also bealtered by using different types of materials and changing the thicknessof the insulating sheath in which the slits are cut to produce thedeployable lobes. The StarFix™ lobes are deployed by pushing theinsulating sheath on either side of the parallel slits. The pushingaction causes the sheath to become compressed, thus causing theextension of the deployable lobes outwardly. As necessary, the lobes canbe relaxed to allow for acute repositioning of the lead by withdrawing acoupling member so as to reduce compression on the lobe structure. TheStarFix™ lead technology provides reliable fixation of medical leadsthat can be readily customized to fit a variety of anatomicaldimensions. Examples of deployable lobe members for biasing and/orstabilizing lead 29 within carotid sheath 156 include those described inU.S. Patent Publication No. 2004/0176782 A1, to George H. Hanse et al.,filed Mar. 3, 2004, titled “METHOD AND APPARATUS FOR FIXATING ANIMPLANTABLE MEDICAL DEVICE,” the entire content of which is incorporatedherein by reference.

The placement of lead 29 adjacent vagus nerve 150 may be stabilized byanchor 172. As explained above, anchor 172 may be any suitable fixationelement that stabilizes the placement of lead 29 and electrodes 170within sheath 156 adjacent vagus nerve 150. In one example, anchor 172includes one or more tines protruding from lead 29 offset from the mostproximate of electrodes 170 by a distance D. The tines of anchor 172 maybe angled with respect to lead 29 and flexible such that as lead 29 isguided forward through tissue of patient 12 the tines lay down againstan exterior surface of the lead and do not engage the tissue of thepatient. After placement, lead 29 may be backed slightly out through thetissue of patient 12 to cause the tines of anchor 172 to pull away fromthe lead and catch and pierce the tissue of patient 12, therebyconnecting lead 29 to the tissue.

In other examples, anchor 172 may include a sleeve anchor configured toreceive lead 29 therethrough and passively engage or be sutured totissue of patient 12. FIGS. 8A-8B show two example sleeve anchors 200and 202 respectively. Both anchors 200 and 202 have interior bore 204that is sized to receive lead 29 therethrough. Anchors 200 and 202 alsoinclude tabs 206 and 208 respectively protruding away from bore 204.Tabs 206 of anchor 200 are configured to passively engage tissue ofpatient 12 to substantially fix the anchor and thereby stabilize theplacement of lead 29. Tabs 208 of anchor 202, on the other hand,includes suture-receiving apertures 210 that may receive sutures toattach anchor 202 to tissue of patient 12 and thereby stabilize theplacement of lead 29. Anchor 202 also includes ribs 212, which may beadapted to inhibit longitudinal movement of anchor 202 and/or lead 29with respect to tissue of patient 12 to further stabilize the placementof lead 29. In some examples, sleeve anchors 200 and 202 may be used toseal a tissue access site, such as incision 174 in carotid sheath 156.

In addition to the above described examples, anchor 172 may includedeployable lobes that are arranged to deploy on either side of incision174 in carotid sheath 156 to stabilize the placement of lead 29 adjacentvagus nerve 150. FIG. 8C shows deployable lobe member 178 arranged atincision 174 in carotid sheath 156 to stabilize placement of lead 29. Aswith the example arrangement shown in FIG. 6, deployable lobe member 178in FIG. 8C includes a plurality of deployable lobes that protrude fromand are circumferentially distributed about lead 29. In FIG. 8C,however, lobe member 178 is arranged with respect to incision 174 suchthat the incision in carotid sheath 156 lies between two sets ofdeployable lobes 178A, 178B of deployable lobe member 178. Deployablelobe set 178A lies adjacent incision 174 outside of carotid sheath 156,while set 178B lies inside the sheath. Upon deployment of lobe sets 178Aand 178B on either side of incision 174, deployable lobe member 178stabilizes the placement of lead 29 and electrodes 170 within sheath 156adjacent vagus nerve 150. As with the example of FIG. 6, an example ofdeployable lobe member 178 arranged as in the example of FIG. 8C may bethe Attain® StarFix™ fixation element developed and sold by Medtronic,Inc. of Minneapolis, Minn.

A portion of lead 29 extending from anchor 172 in the examples of FIGS.6-8C may be guided to connect with IMD 16. In one example, lead 29 maybe guided intravascularly to an implantation location of IMD 16 withinpatient 12. In other examples, lead 29 may be tunneled through tissue ofpatient 12 to be connected to IMD 16. Although the example of FIGS. 6and 7 is described with reference to implanted medical device 16arranged within patient 12, examples according to this disclosure alsoinclude lead 29 connected transcutaneously to an external medical devicethat is configured to deliver electrical stimulation to the target nervetissue, e.g., vagus nerve 150. After lead 29 is placed adjacent vagusnerve 150 and connected to IMD 16, IMD 16, either automatically or aspartially or completely commanded by programmer 24, may deliverelectrical stimulation therapy to and/or receive sensor feedback fromvagus nerve 150 through electrodes 170.

Intravascular lead placement proximate target nerve tissue within apatient generally requires minimally invasive surgical techniquesbecause the medical leads used to deliver therapy are guided to the sitethrough a blood vessel, e.g., a vein or artery that may be readilyaccessible, e.g., transcutaneously through a small incision.Intravascular lead placement techniques disclosed herein furtherfacilitate placing the distal end of the lead in close proximity of thetarget nerve tissue, which can be arranged in different circumferentialpositions with respect to the blood vessel in which the lead is located.

Intravascular techniques described in greater detail below may includestructures and methods for deployment of one or more medical leads at afirst location, testing stimulation at the first location, and,depending on the efficacy of the stimulation provided by electrodes onthe leads at the first location, redeploying the leads to a secondlocation. In one example, lead placement is improved by locating targetnerve tissue with a sensor including, e.g., an IVUS imaging systemsystem and/or measuring the efficacy of test electrical stimulationpulses from an electrode on the lead through a blood vessel adjacent thetarget tissue. After a placement location is determined, one or moreleads including one or more electrodes may be deployed into the vesseland anchored to a vessel wall near the target nerve tissue.

FIGS. 9 and 10 illustrate examples of intravascular lead placementtechniques in the context of vagal nerve stimulation in a human patient.FIG. 9 is a schematic illustration depicting lead 29 intravascularlyplaced adjacent vagus nerve 150 within internal jugular vein 158 inpatient 12. After or during placement, lead 29 may be connected to IMD16 or INS 26 similar to lead 28 shown in FIGS. 1A and 1B respectively.FIG. 10 is a flow chart illustrating an example method of placing lead29 in accordance with the example of FIG. 9. The example method of FIG.10 includes deploying a delivery catheter through a lumen of a bloodvessel to a target nerve tissue site (240), identifying a location ofthe nerve tissue with respect to the blood vessel with one or moresensors connected to the delivery catheter (242), advancing anelectrical stimulation electrode from the catheter within the bloodvessel lumen toward the nerve tissue (244), energizing the electrode todeliver electrical stimulation from within the blood vessel lumen to thenerve tissue (246), comparing the efficacy of the nerve tissuestimulation to a threshold efficacy (248), and repositioning thedelivery catheter and the electrode within the blood vessel lumen if theefficacy of the nerve tissue stimulation does not meet or exceed thethreshold efficacy (250), or chronically deploying the electrode withinthe blood vessel lumen adjacent the nerve tissue if the efficacy of thenerve tissue stimulation meets or exceeds the threshold efficacy (252).One example of the method illustrated in FIG. 10 will be described inthe context of the example lead placement structure shown in FIG. 9.

The arrangement shown in FIG. 9 includes delivery catheter 220, sensor222, and deployment member 224. Sensor 222 is connected to catheter 220toward a distal end thereof. Deployment member 224 is extendable andretractable from catheter 220. Sensor 222 is arranged between the distalend of catheter 220 and the location along catheter 220 from whichdeployment member 224 is extendable and retractable. Deployment member224 includes tubular member 226, lead 29, electrode 228, and guidewire230. Guidewire 230 includes anchor portion 230A at a distal end thereof.Electrode 228 is connected toward a distal end of lead 29. Lead 29 andguidewire 230 are received within and advanceable through a lumen oftubular member 226. Lead 29 is advanceable along guidewire 230.

In FIG. 9, catheter 220 is deployed through internal jugular vein 158 ofpatient 12 to a target nerve tissue stimulation site. In other examples,catheter 220 may be deployed in other blood vessels within patient 12including, e.g., carotid artery 160, or the superior or inferior venacava. Catheter 220 can be any suitable delivery catheter capable ofintravenous delivery within patient 12 and adapted to accommodate sensor222 and deployment member 224. Sensor 222 is connected to the distal endof catheter 220 and is configured to detect the relative position ofvagus nerve 150 outside of jugular vein 158, as well as electrode 228 onlead 29 within the lumen of vein 158. Sensor 222, in general, may be anysuitable imaging or guidance system including, e.g., a fiberopticendoscope, ultrasound imaging system, or any other on-board imagingsystem capable of assisting in the positioning of catheter 220 andelectrode 228 within jugular vein 158 relative to vagus nerve 150 byproviding an image of the area adjacent the location of sensor 222 oncatheter 220. In some examples, sensor 222 could be an array ofreceivers in relationship to a transmitter that provide an image ofsurrounding tissue and structures including vagus nerve 150 andelectrode 228. In other examples, sensor 222 may be configured to sendor receive signals to or from any of a series of known signal generatorsincluding sonic, electromagnetic, light or radiation signals. In stillother examples, sensor 222 may be an optical oxygen content sensor thatmay be used to ensure that lead 29 and electrode 228 are not directedtoward, e.g., carotid artery 160 during lead placement. In someexamples, sensor 222 may be employed in conjunction with one or moreopaque markers viewable with fluoroscopic techniques or with anirrigated lumen that dispenses contrast media to assist in imaging therelative positions of vagus nerve 150 and electrode 228 on lead 29within the lumen of jugular vein 158.

After the clinician identifies the location of vagus nerve 150 withrespect to jugular vein 158 based on the output of sensor 222, theclinician may advance deployment member 224 including electrode 228toward the wall of the lumen of vein 158 adjacent the nerve. Deploymentmember 224, in general, is extendable and retractable from catheter 220from, e.g., an aperture formed in a sidewall thereof. Deployment member224 includes tubular member 226, lead 29, electrode 228, and guidewire230. Tubular member 226 may be any structure including at least onelumen through which various electrode deployment structures including,e.g., lead 29 and guidewire 230 may be advanced to place an electrodewithin vein 158 adjacent vagus nerve 150. In the example of FIG. 9,tubular member 226 may be a needle with a lumen in which lead 29 andguidewire 230 are received and through which the same are advanceable.Electrode 228 is connected to lead 29, which is advanceable alongguidewire 230.

With the aid of sensor 222, the clinician advances deployment member 224from catheter 220 toward vagus nerve 150. Lead 29, to which electrode228 is connected, and guidewire 230 may be advanced through a lumen ofdeployment member 224 to position electrode 228 within vein 158 adjacentvagus nerve 150. Guidewire 230 includes anchor portion 230A at a distalend thereof that is configured to temporarily anchor deployment member224, lead 29 and electrode 228, and guidewire 230 to the wall of thelumen of vein 158. In the example of FIG. 9, anchor portion 230A ofguidewire 230 is formed in a spiral that is configured to be twistedinto the lumen wall. Anchor portion 230A can be freed from the vesselwall by either untwisting guidewire 230, or in the case that guidewire230 is sufficiently flexible, pulling the wire away from the spiralinganchor portion 230A to effectively unwind and release the anchor fromthe wall of jugular vein 158. In addition to anchor portion 230A ofguidewire 230, lead 29 includes barbs 231 that are configured to engagetissue of jugular vein 158 to anchor lead 29 and electrode 228 to thewall of the vein after guidewire 230 has been retracted. In otherexamples, lead 29 may be anchored to the wall of vein 158 with differentstructures including, e.g., a helical coil or other spiral coil shapes,C-shaped members, harpoon-like structures, hooks, expandable or serratedmembers, and the like. In FIG. 9, deployment member 224 and electrode228 on lead 29 are advanced such that at least lead 29 lies in thesensory field of sensor 222.

In one example, sensor 222 is an intravenous ultrasound (“IVUS”) imagingsystem that is adapted to radiate ultrasonic waves out from sensor 222to generate a two dimensional image of the tissue and structuressurrounding catheter 220 and sensor 222. FIG. 11 is a schematicillustration of an example two dimensional ultrasonic image generated bya device coupled to sensor 222 as arranged with catheter 220, lead 29and electrode 228 of FIG. 9 located within the jugular vein 158. Whenactivated, sensor 222 produces an imaging field 260 from ultrasonicwaves produced by and radiating radially from sensor 222. The size ofimaging field 260 may vary depending on the particular configuration andcapabilities of sensor 222. The tissues and other structures caughtwithin imaging field 260 of sensor 222 may be distinguished from oneanother and the relative positioning of the different structures may bediscerned. In the example of FIG. 11, vagus nerve 150, jugular vein 158,and carotid artery 160 are located within imaging field 260, whilecarotid sheath 156 shown in shadow lines is not within the sensing rangeof sensor 222. By distinguishing different structures and displayingrelative positions, sensor 222 may be used to facilitate positioningcatheter 220 and electrode 228 on lead 29 within jugular vein 158 in adesired location relative to vagus nerve 150 by, e.g., rotating thecatheter and electrode within the blood vessel in the directionsindicated by arrow 262 in FIG. 11.

Having deployed catheter 220, detected the location of vagus nerve 150relative to jugular vein 158, and advanced electrode 228 toward vagusnerve 150, electrical stimulation may be delivered to vagus nerve 150through the wall of the lumen of vein 158 via electrode 228. During teststimulation of vagus nerve 150, a portion of lead 29 extending away froma distal end toward which electrode 228 is arranged may be connected,e.g., transcutaneously to an external neurostimulation device that isconfigured to deliver electrical stimulation to the target nerve tissue,e.g., vagus nerve 150 while lead 29 and electrode 228 are beingpositioned relative thereto within vein 158. After lead 29 is connectedto the neurostimulator, the device, either automatically or as partiallyor completely commanded by a programmer, such as programmer 24, maydeliver electrical stimulation therapy to and/or receive sensor feedbackfrom vagus nerve 150 through electrode 228.

In the example of FIGS. 9 and 10, as well as other examples disclosedherein, the efficacy of the electrical stimulation delivered byelectrode 228 to vagus nerve 150 may be compared to a threshold efficacyto determine whether or not electrode 228 is satisfactorily positionedwith respect to nerve 150. Efficacy refers, in general, to a combinationof complete or partial alleviation of symptoms alone, or in combinationwith a degree of undesirable side effects. Efficacy may be measured, ingeneral, by verbal feedback from patient 12, clinician observation ofvarious conditions of patient 12, or sensory feedback from one or moredevices including, e.g., ICD 17 shown in FIG. 1A or cardiac therapymodule 104 shown in FIG. 4. Various physiological signals may beobserved to measure the efficacy of the test stimulation, and therebythe need to reposition lead 29 relative vagus nerve 150. For example, todetermine the response to stimulation of vagus nerve 150, ECG, heartrate, blood pressure, blood flow, cardiac output, and/or breathing, ofpatient 12 can be sensed or observed. These and other physiologicalsignals may be detected in a variety of ways including sensing thesignals using sense electrodes, pressure sensors, ultrasound sensors,motion sensors or other devices. In other examples, physiologicalreactions of patient 12 may be observed or measured by, e.g., aclinician. In one example, efficacy may be measured by a sensorincluding, e.g., an accelerometer that determines if stimulation of theneck muscles or phrenic nerve of patient 12 is occurring with or insteadof stimulation of vagus nerve 150. In another example, a pressure sensorarranged coincident with or connected to lead 29 may measure bloodpressure by detecting the pressure within jugular vein 158. A pressuresensor, or other type of physiological feedback sensor, may also, insome examples, be connected to catheter 220 to measure, e.g., bloodpressure within vein 158.

In the event the nerve tissue stimulation meets or exceeds the thresholdefficacy, lead 29 and electrode 228 may be chronically deployed withinjugular vein 158 adjacent vagus nerve 150. On the other hand, if thenerve stimulation delivered by electrode 228 does not provide thethreshold level of efficacy in relieving the symptoms of patient 12,catheter 220 and electrode 228 may be repositioned within jugular vein158 to improve the location of the components, in particular electrode228 with respect to vagus nerve 150. Generally speaking, catheter 220and electrode 228 may be repositioned by rotating catheter 220 withinjugular vein 158 in the manner described with reference to FIG. 11 andwith the assistance of, e.g., ultrasound imaging provided by sensor 222.In some examples, guidewire 230 including anchor portion 230A may beretracted along with lead 29 and electrode 228 into deployment member224 before repositioning catheter 220 and then redeployed after thecatheter has be relocated. After repositioning catheter 220 andelectrode 228, the process of stimulating vagus nerve 150 and comparingthe efficacy of the nerve stimulation to a threshold efficacy may berepeated until the arrangement of electrode 228 with respect to vagusnerve 150 delivers electrical stimulation therapy that meets or exceedsthe threshold efficacy level.

After determining a placement location that delivers satisfactorytreatment efficacy, lead 29 and electrode 228 may be chronicallydeployed within jugular vein 158 adjacent vagus nerve 150. After chronicdeployment of lead 29 and electrode 228, a portion of lead 29 extendingaway from a distal end toward which electrode 228 is arranged may beguided to connect with, e.g., IMD 16. In one example, lead 29 may beguided intravascularly to an implantation location of IMD 16 withinpatient 12. In other examples, lead 29 may be tunneled through tissue ofpatient 12 to be connected to IMD 16. After lead 29 is placed adjacentvagus nerve 150 and connected to IMD 16, IMD 16, either automatically oras partially or completely commanded by programmer 24, may deliverelectrical stimulation therapy to and/or receive sensor feedback fromvagus nerve 150 through electrode 228.

FIGS. 12A and 12B show alternative examples of deployment member 224 foruse in methods and systems according to this disclosure. In general,FIGS. 12A and 12B show different arrangements and combinations ofanchoring members and electrodes with respect to tubular member 226,lead 29, and guidewire 230 of deployment member 224. In the interest ofsimplicity, catheter 220 has been omitted from the illustrations ofFIGS. 12A and 12B. In FIG. 12A, deployment member 224 is arranged withinjugular vein 158 adjacent vagus nerve 150 and includes tubular member226, lead 29, electrode 228, guidewire 230, and expandable member 270.In some examples, expandable member 270 may provide additionalstabilization or biasing of lead 29 or other components of deploymentmember 224 within jugular vein 158. For example, expandable member 270may push against catheter 220 (not shown in FIG. 12A) to bias lead 29and electrode 228 toward the wall of the lumen of vein 158. In anotherexample, expandable member 270 may further stabilize the placement oflead 29 and electrode 228 by expanding to apply force on the lumen walland catheter 220. The expandable member 270 may, in some examples, be aballoon catheter including, e.g., an angioplasty catheter. In otherexamples, expandable member 270 may be a stent or deployable spline orlobe.

FIG. 12B shows deployment member 224 with additional electrode 272connected to tubular member 226. In FIG. 12B, deployment member 224 isarranged within jugular vein 158 adjacent vagus nerve 150 and includestubular member 226, lead 29, electrode 228, guidewire 230, and electrode272. Although intravascular placement examples of lead 29 have beendescribed herein with reference to a single electrode 228 forsimplicity, in practice, lead 29 will commonly include a plurality ofelectrodes that may be employed in different anode and cathodecombinations to stimulate vagus nerve 150 as, e.g., described withreference to electrodes 80-83 in FIG. 2. Additionally and as illustratedin FIG. 12B, deployment member 224 may include electrodes in addition tolead electrode 228 arranged in different locations and/or connected todifferent components. Electrode 272 is connected to tubular member 226in the example of FIG. 12B. In some examples, tubular member 226 andelectrode 272 may be advanced toward vagus nerve 150 prior tochronically deploying lead 29 and electrode 228. In such examples,electrode 272 may be used to deliver test stimulation pulses to vagusnerve 150 to determine the efficacy of the placement of deploymentmember 224 within jugular vein 158 with respect to vagus nerve 150.After determining a position of deployment member that provides athreshold efficacy in stimulating vagus nerve 150, lead 29 and guidewire230 may be advanced through tubular member 226 and lead 29 and electrode228 may be chronically deployed along the wall of the lumen of jugularvein 158 adjacent vagus nerve 150.

In addition to placing lead 29 and electrode 228 intravascularly usingdeployment member 224 as shown in the examples of FIGS. 9, 11, 12A and12B, lead 29 and electrode 228 may be advanced from a distal tip ofcatheter 220 to be actively fixed to the wall of jugular vein 158 asshown in FIG. 13. The arrangement shown in FIG. 13 includes deliverycatheter 220, sensor 222, lead 29, electrodes 228 and 229, and activefixation member 274. Sensor 222 and electrode 229 are connected tocatheter 220 toward a distal end thereof. Electrode 228 is connectedtoward a distal end of lead 29. Lead 29 and electrode 228 are receivedwithin and advanceable through a lumen of catheter 220 and out of thetip of the catheter to place electrode 228 within vein 158 adjacentvagus nerve 150. Although not shown in FIG. 13, lead 29 may be advancedalong and guided by a guide member including, e.g., a guidewire or astylus.

In FIG. 13, catheter 220 is deployed through internal jugular vein 158of patient 12 to a target nerve tissue stimulation site. In otherexamples, catheter 220 may be deployed in other blood vessels withinpatient 12 including, e.g., carotid artery 160, or the superior orinferior vena cava. Catheter 220 can be any suitable delivery cathetercapable of intravenous delivery within patient 12 and adapted toaccommodate sensor 222, electrode 229, and lead 29. In some examples,catheter 220 may be flexible or curved to direct the tip of the catheterlaterally toward the wall of jugular vein 158. Sensor 222 is connectedto the distal end of catheter 220 and is configured to detect therelative position of vagus nerve 150 outside of jugular vein 158. Sensor222, in general, may be any suitable imaging or guidance systemincluding, e.g., a fiberoptic endoscope, ultrasound imaging system, orany other on-board guidance or imaging system capable of assisting inthe positioning of catheter 220 within jugular vein 158 relative tovagus nerve 150 by providing an image of the area adjacent the locationof sensor 222 on catheter 220.

Electrode 229 is also connected to a distal end of catheter 220 and maybe advanced toward the wall of the lumen of jugular vein 158 to delivertest stimulation pulses to vagus nerve 150 through the wall of vein 158.Electrode 229 may therefore be employed in addition to or in lieu ofsensor 222 to detect the relative position of vagus nerve 150 outside ofjugular vein 158. During test stimulation of vagus nerve 150, electrode229 may be connected to a conductor connected, e.g., transcutaneously toan external neurostimulation device that is configured to deliverelectrical stimulation to the target nerve tissue, e.g., vagus nerve150. After electrode 229 is connected to the neurostimulator, thedevice, either automatically or as partially or completely commanded bya programmer, such as programmer 24, may deliver electrical stimulationtherapy to and/or receive sensor feedback from vagus nerve 150.

In the example of FIG. 13, as well as other examples disclosed herein,the efficacy of the electrical stimulation delivered by electrode 229 tovagus nerve 150 may be compared to a threshold efficacy to determinewhether or not electrode 229, and thereby catheter 220 is satisfactorilypositioned with respect to nerve 150. Efficacy may be measured, ingeneral, by verbal feedback from patient 12, clinician observation ofvarious conditions of patient 12, or sensory feedback from one or moredevices including, e.g., ICD 17 shown in FIG. 1A or cardiac therapymodule 104 shown in FIG. 4. Various physiological signals may beobserved to measure the efficacy of the test stimulation, and therebythe need to reposition catheter 220 and electrode 229 relative vagusnerve 150. For example, to determine the response to stimulation ofvagus nerve 150, ECG, heart rate, blood pressure, blood flow, cardiacoutput, and/or breathing, of patient 12 can be sensed or observed. Theseand other physiological signals may be detected in a variety of waysincluding sensing the signals using sense electrodes, pressure sensors,ultrasound sensors, motion sensors or other devices. In other examples,physiological reactions of patient 12 may be observed or measured by,e.g., a clinician. In one example, efficacy may be measured by a sensorincluding, e.g., an accelerometer that determines if stimulation of theneck muscles or phrenic nerve of patient 12 is occurring with or insteadof stimulation of vagus nerve 150. In another example, a pressure sensorarranged coincident with or connected to catheter 220 may measure bloodpressure by detecting the pressure within jugular vein 158.

In the event the nerve tissue stimulation meets or exceeds the thresholdefficacy, lead 29 and electrode 228 may be chronically deployed byadvancing the lead from the tip of catheter 220 within jugular vein 158toward vagus nerve 150. On the other hand, if the nerve stimulationdelivered by electrode 229 does not provide the threshold level ofefficacy in relieving the symptoms of patient 12, catheter 220 andelectrode 229 may be repositioned within jugular vein 158 to improvelocation with respect to vagus nerve 150. Generally speaking, catheter220 and electrode 229 may be repositioned by rotating catheter 220within jugular vein 158 to different incremental positions until anacceptable position for catheter 220 relative to vagus nerve 150 isdetermined. After repositioning catheter 220 and electrode 229, theprocess of stimulating vagus nerve 150 and comparing the efficacy of thenerve stimulation to a threshold efficacy may be repeated until thearrangement of catheter 220 with respect to vagus nerve 150 deliverselectrical stimulation therapy that meets or exceeds the thresholdefficacy level.

Once catheter 220 is positioned within jugular vein 158 such thatelectrode 229 delivers stimulation that meets or exceeds the thresholdefficacy, lead 29 and electrode 228 may be advanced through a lumen ofcatheter 220 and out of the tip of the catheter to actively fix lead 29and electrode 228 to the wall of vein 158 adjacent vagus nerve 150. InFIG. 13, catheter 220 is curved to direct the tip of the catheterlaterally toward the wall of jugular vein 158. Connected to a distal endof lead 29 is active fixation member 274, which, in the example of FIG.13 is a helical coil that is configured to be twisted into the wall ofjugular vein 158.

In practice, lead 29, electrode 228, and fixation member 274 may beadvanced laterally from the tip of catheter 220 toward the wall ofjugular vein 158 adjacent vagus nerve 150. In some examples, lead 29 maybe directed toward the wall of vein 158 along a trajectory that isapproximately perpendicular to the wall. Active fixation member 274engages the wall of the lumen of jugular vein 158 by, e.g., twistinglead 29 to screw the helical fixation member into the wall. Afteractively fixing lead 29 and electrode 228 to the wall of vein 158adjacent vagus nerve 150, catheter 220 may be removed, after which lead29 and electrode 228 will lay down along and approximately tangential tothe wall of vein 158.

In some examples, active fixation member 274 may be electrically activesuch that it acts as an electrode in addition to or in lieu of electrode228. Fixation member 274 may have a variety of lengths and helicalpitches. In some examples, fixation member 274 may have a length in therange from and including approximately 0.5 millimeters to and includingapproximately 2.5 millimeters. In other examples, fixation member 274may have a length in the range from and including approximately 1millimeters to and including approximately 2 millimeters. The pitch ofthe helical coil of active fixation member 274 may also vary indifferent examples according to this disclosure. In general, in examplesin which fixation member 274 is electrically active, it may be desirableto increase the pitch to increase the amount of surface area engagingtissue of the wall of jugular vein 158. In some examples, fixationmember 274 may have a helical pitch in the range from and includingapproximately 0.5842 millimeters to and including approximately 1.016millimeters.

FIGS. 14A-14J are elevation front views of various anchors that may beused alone or in combination to anchor or bias a medical lead and/orelectrode within a vessel in accordance with examples disclosed herein.The anchors illustrated in FIGS. 14A-14J may be employed, for example,in a manner as described with reference to anchor portion 230A ofguidewire 230 and/or barbs 231 in FIG. 9. In such examples, anchorportion 230A of guidewire 230 and/or barbs 231 may take an alternativeform to that shown in FIG. 9 including, e.g., the harpoon shapes ofFIGS. 14B and 14C. In another example, a portion of lead 29 may beshaped as shown in FIG. 14A, 14D, or 14F and wedged into jugular vein158 to anchor the lead and electrode 228 within the vein adjacent vagusnerve 150.

In addition to the intravascular techniques described with reference toFIGS. 9-14, examples according to this disclosure also includetechniques employing an expandable and contractible generallycylindrical lead member that is temporarily deployable for testingmultiple electrode orientations and combinations before deploying themember for chronic stimulation of target nerve tissue within a patient.

FIGS. 15 and 16 illustrate examples of intravascular lead placementtechniques including a generally cylindrical expandable and contractiblelead member in the context of vagal nerve stimulation in a humanpatient. FIG. 15 is a schematic illustration depicting lead 29 attachedto cylindrical lead member 300, both of which are intravascularly placedadjacent vagus nerve 150 within internal jugular vein 158 in patient 12.After or during placement, lead 29 and lead member 300 may be connectedto IMD 16 or INS 26 similar to lead 28 shown in FIGS. 1A and 1Brespectively. FIG. 16 is a flow chart illustrating an example method ofplacing lead 29 and cylindrical lead member 300 in accordance with theexample of FIG. 15. The example method of FIG. 16 includes arranging agenerally cylindrical expandable and contractible lead member within alumen of a blood vessel adjacent target nerve tissue (310), temporarilydeploying the cylindrical lead member within the lumen relative to thenerve tissue (312), energizing one or more electrodes connected to thecylindrical lead member to deliver electrical stimulation from withinthe blood vessel lumen to the nerve tissue (314), comparing the efficacyof the nerve tissue stimulation to a threshold efficacy (316), andredeploying the cylindrical lead member within the lumen relative to thenerve tissue if the efficacy of the nerve tissue stimulation does notmeet or exceed the threshold efficacy (318), or chronically deployingthe cylindrical lead member in an expanded state within the lumen if theefficacy of the nerve tissue stimulation meets or exceeds the thresholdefficacy (320). One example of the method illustrated in FIG. 16 will bedescribed in the context of the example lead structure shown in FIG. 15.

The arrangement shown in FIG. 15 includes lead member 28, cylindricallead member 300, and electrodes 302. As will be described in greaterdetail below, some examples may include additional components forarranging and deploying cylindrical lead member 300 within a bloodvessel including, e.g., a delivery catheter and/or a stylus or otheractive deployment mechanism. Cylindrical lead member 300 is connected toa distal end of lead member 28. Electrodes 302 are connected to anexterior surface of lead member 300 and are arranged in columns 304parallel to a longitudinal axis of lead member 300. Depending on howelectrodes 302 are grouped, they may also be seen in FIG. 15 as arrangedin columns 306 that wrap around the exterior surface of lead member 300oriented at an angle with respect to the longitudinal axis of thecylindrical lead member. In other examples according to this disclosure,lead member 300 may include fewer or more electrodes 302 than shown inthe example of FIG. 15. For example, lead member 302 may include morethan two columns 306 of electrodes 302 distributed circumferentiallyaround the exterior surface of cylindrical lead member 300. Cylindricallead member 300 is an expandable and retractable component that may bedeployed and redeployed passively or actively within a blood vessel.Lead member 300 is shown schematically in FIG. 15 in a contracted statein dashed lines and in an expanded state in solid lines. As described ingreater detail below, cylindrical lead member 300 may be any one of anumber of different structures that are capable of active and/or passivedeployment and redeployment including, e.g., circular cylindricalmembers, wire mesh stents, and spiral wire and ribbon members.

In FIG. 15, lead 29 and cylindrical lead member 300 are arranged withinthe lumen of internal jugular vein 158 adjacent vagus nerve 150. Inother examples, lead member 300 may be deployed in other blood vesselswithin patient 12 including, e.g., carotid artery 160 adjacent vagusnerve 150 or another vein or artery adjacent the target nerve tissue atwhich stimulation therapy is directed. Cylindrical lead member 300 maybe guided to the target nerve tissue site within patient 12 by, e.g., asmall transcutaneous incision to gain access to jugular vein 158 andthen directed through the vein by, e.g., a delivery catheter to thetarget site adjacent vagus nerve 150.

After arranging cylindrical lead member 300 within the lumen of jugularvein 158 adjacent vagus nerve 150, lead member 300 may be temporarilydeployed within the lumen relative to vagus nerve 150. Vagus nerve 150is positioned within patient 12 outside of jugular vein 158, which has agenerally tubular shape. Upon intravascular implantation of lead member300 within jugular vein 158, the relative orientation of vagus nerve 150around the periphery of jugular vein 158 may not be known without, e.g.,complete dissection of carotid sheath 156. Deployment of lead member 300within jugular vein 158 and stimulation of vagus nerve 150 by selectedones of electrodes 302 may initially be somewhat arbitrary with respectto the actual position of vagus nerve 150 without testing or feedbackregarding the orientation and combination of electrodes 302 used.Therefore, cylindrical lead member 300 is capable of deployment andredeployment within jugular vein 158 adjacent vagus nerve 150 to testmultiple orientations and combinations of electrodes 302 beforedeploying the lead member for chronic treatment of patient 12.

As indicated in FIG. 15 by arrow 308, lead member 300 is capable ofbeing rotated within jugular vein 158 to vary the orientation of leadmember 300, and thereby electrodes 302 within the vein. Lead member 300may be oriented within jugular vein 158 both by rotating the lead memberand also may be, in some examples, temporarily expanded to abut thewalls of the lumen of vein 158 as shown in FIG. 15. In addition toorienting and expanding lead member 300, electrodes 302 may beselectively activated in different combinations in a manner similar tothat described with reference to FIG. 2. For example, lead 29 andcylindrical lead member 300 may be connected to IMD 16 shown in FIGS. 1Aand 2. Neurostimulation therapy module 106 of IMD 16 may include aswitching module to selectively couple pairs of electrodes 302 to signalgenerator 112 and/or sensing module 114 to form different anode-cathodecombinations. The switching module may include, e.g., a switch array,switch matrix, multiplexer, or any other type of switching devicesuitable to selectively couple stimulation energy to selectedelectrodes. In one example, the switching module may select combinationsof electrodes 302 grouped along longitudinal column 304 in FIG. 15. Inanother example, however, the switching module may select combinationsof electrodes 302 grouped along the skewed columns 306. In this manner,deploying lead member 300 within the lumen of jugular vein 158 mayinclude both orienting and expanding lead member 300 and electrodes 302within the vein, and selecting combinations of electrodes 302 tostimulate (and/or sense nerve signals from) vagus nerve 150. During theplacement of lead member 300, lead 29 may be transcutaneously connectedto IMD 16 to test the placement of lead member 300 prior to implantingthe device within patient 12. In another example, lead 29 may beconnected to an external neurostimulation device that is configured todeliver electrical stimulation to vagus nerve 150 while lead member 300is being positioned relative thereto within vein 158.

After cylindrical lead member 300 and electrodes 302 have beentemporarily deployed within jugular vein 158, one or more of theelectrodes may be energized to deliver electrical stimulation to vagusnerve 150. During test stimulation of vagus nerve 150, a portion of lead29 extending away from a distal end to which lead member 300 andelectrodes 302 may be connected, e.g., transcutaneously to an externalneurostimulation device that is configured to deliver electricalstimulation to the target nerve tissue, e.g., vagus nerve 150 while leadmember 300 and electrodes 302 are being positioned relative theretowithin vein 158. After cylindrical lead member 300 is placed adjacentvagus nerve 150 and connected to the external neurostimulator, thedevice, either automatically or as partially or completely commanded bya programmer, such as programmer 24, may deliver electrical stimulationtherapy to and/or receive sensor feedback from vagus nerve 150 throughone or more of electrodes 302.

In the example of FIGS. 14 and 15, as well as other examples disclosedherein, the efficacy of the electrical stimulation delivered byelectrodes 302 to vagus nerve 150 may be compared to a thresholdefficacy to determine whether or not cylindrical lead member 300 andelectrodes 302 are satisfactorily positioned with respect to nerve 150and/or an optimal combination of electrodes 302 has been selected todeliver stimulation to the nerve. As described above with reference toFIGS. 9 and 10, efficacy may be measured, in general, by verbal feedbackfrom patient 12, clinician observation of various conditions of patient12, or sensory feedback from one or more sensors. Various physiologicalsignals may be observed to measure the efficacy of the test stimulation,and thereby the need to reposition lead member 300 relative vagus nerve150. For example, to determine the response to stimulation of vagusnerve 150, ECG, heart rate, blood pressure, blood flow, cardiac output,and/or breathing, of patient 12 can be sensed or observed.

In the event the nerve tissue stimulation meets or exceeds the thresholdefficacy, cylindrical lead member 300, to which electrodes 302 areattached, may be chronically deployed in an expanded state withinjugular vein 158 adjacent vagus nerve 150. The orientation ofcylindrical lead member 300 and selected combination of electrodes 302that delivered therapy to patient 12 meeting or exceeding the thresholdefficacy may be used to deliver chronic, i.e. long term therapy to thepatient. On the other hand, if the nerve stimulation delivered bycylindrical lead member 300 and electrodes 302 does not provide thethreshold level of efficacy in treating patient 12, lead member 300 maybe redeployed within jugular vein 158 relative to vagus nerve 150. Aswith the initial temporary deployment, redeploying lead member 300 mayinclude orienting the lead member by rotating within jugular vein 158,as well as selecting one or more combinations of electrodes 302 tostimulate vagus nerve 150. In some examples of redeployment, lead member300 may also be contracted and then re-expanded to abut the walls of thelumen of jugular vein 158 as shown in FIG. 15. For example, in the eventlead member 300 was previous expanded within jugular vein 158, the leadmember may need to be contracted in order to be reoriented by rotatingit within the vein. After redeploying cylindrical lead member 300, theprocess of stimulating vagus nerve 150 and comparing the efficacy of thenerve stimulation to a threshold efficacy may be repeated until thearrangement of lead member 300 with respect to vagus nerve 150 deliverselectrical stimulation therapy that meets or exceeds the thresholdefficacy level.

After determining a placement location that delivers satisfactorytreatment efficacy, cylindrical lead member 300, to which electrodes 302are attached, may be chronically deployed in an expanded state withinjugular vein 158 adjacent vagus nerve 150. After chronic deployment oflead member 300, a portion of lead 29 extending away from a distal endtoward which lead member 300 is arranged may be guided to connect with,e.g., IMD 16. In one example, lead 29 may be guided intravascularly toan implantation location of IMD 16 within patient 12. In other examples,lead 29 may be tunneled through tissue of patient 12 to be connected toIMD 16. After lead 29 is placed adjacent vagus nerve 150 and connectedto IMD 16, IMD 16, either automatically or as partially or completelycommanded by programmer 24, may deliver electrical stimulation therapyto and/or receive sensor feedback from vagus nerve 150 throughelectrodes 302.

FIGS. 17A and 17B, and 18A-18D show several examples of cylindrical leadmember 300 and delivery mechanisms appropriate for use in the example ofFIGS. 15 and 15. FIGS. 17A and 17B are schematic illustrations of acylindrical lead member arranged within a delivery catheter fordeploying and redeploying the lead member within jugular vein 158relative to vagus nerve 150. FIGS. 18A-18D are schematic illustrationsof different examples of a cylindrical lead member that is expandableand contractible for deployment and redeployment within vein 158.

Generally speaking, there are several methods by which cylindrical leadmember 300 may be temporarily and then chronically deployed within ablood vessel to test various orientations and combinations of electrodes302 relative to vagus nerve 150. In some examples, cylindrical leadmember 300 may be arranged adjacent vagus nerve 150 within a deliverymechanism that allows for the flexible orientation and selection ofcombinations of electrodes 302 within jugular vein 150 relative to theposition of vagus nerve 150. For example, lead member 300 may bearranged within a delivery catheter that accommodates relative movementof the lead member and the catheter to expose different combinations ofelectrodes 302 oriented in different positions within vein 158 relativeto vagus nerve 150. In other examples, cylindrical lead member 300 maybe actively expandable and contractible such that the lead member may beexpanded within jugular vein 158 and thereafter contracted andre-expanded in a different orientation relative to vagus nerve 150.

FIGS. 17A and 17B are schematic illustrations of a cylindrical leadmember arranged within a delivery catheter that accommodates relativemovement of the lead member and the catheter to expose differentcombinations of electrodes 302 oriented in different positions withinvein 158 relative to vagus nerve 150. In FIG. 17A, lead 29 andcylindrical lead member 300 connected thereto are arranged withindelivery catheter 330. Electrodes 302 are connected to lead member 300and arranged in columns 304 that are generally parallel to alongitudinal axis of the lead member. Catheter 330 includes a pluralityof apertures 332 that are shaped and sized to expose groups ofelectrodes 302. In the example of FIG. 17A, apertures 332 are generallyrectangular slots in catheter 330. However, in other example, apertures332 may be, e.g., holes arranged to expose one or more of electrodes302.

In practice, delivery catheter 330 and lead member 300 may be guidedintravascularly to a target tissue site through jugular vein 158adjacent vagus nerve 150. Cylindrical lead member 300 may be orientedwithin catheter 330 such that select groups of electrodes 302 areexposed by apertures 332. In the example of FIG. 17A, electrodes 302will be generally exposed in groups arranged along longitudinal columns304. However, in other examples, apertures 332 may be shaped andoriented to expose one or more electrodes 302 in different groupsincluding, e.g., groups arranged along columns oriented at an angle withrespect to a longitudinal axis of lead member 300, such as columns 306shown in FIG. 15. In any event, after lead member 300 and electrodes 302are oriented within catheter 330, different combinations of electrodes302 may deliver electrical stimulation to vagus nerve 150. Cylindricallead member 300 and/or catheter 330 may be reoriented within jugularvein 158 one or more times to test different orientations andcombinations of electrodes 302 until a threshold efficacy is indicated.Thereafter, cylindrical lead member 300 and electrodes 302 may bechronically deployed in an expanded state by, e.g., withdrawing deliverycatheter 330 to allow lead member 300 to passively expand to abut thewalls of the lumen of jugular vein 158.

In FIG. 17B, cylindrical lead member 340 is arranged within deliverycatheter 342. Electrodes 344 are connected to lead member 340.Electrodes 344 are ring electrodes arranged around the exterior surfaceof and distributed longitudinally along lead member 340. Catheter 342includes helical aperture 346 that is shaped and sized to exposeportions of each of electrodes 340 at different rotational orientationswithin a blood vessel. In the example of FIG. 17A, apertures 346 is agenerally rectangular slot in catheter 342. However, in other examples,catheter 342 may include a series of holes arranged in a helical line toexpose different portions of electrodes 344 oriented at differentrotational positions.

Similar to the example of FIG. 17A, delivery catheter 342 and leadmember 340 may be guided intravascularly to a target tissue site throughjugular vein 158 adjacent vagus nerve 150. Cylindrical lead member 340may be oriented within catheter 342 such that select portions ofelectrodes 344 are exposed at different rotational orientations withrespect to vagus nerve 150. After lead member 340 and electrodes 344 areoriented within catheter 346, different combinations of electrodes 344may deliver electrical stimulation to vagus nerve 150. Catheter 346 maythen be rotated relative to lead member 340 within jugular vein 158 oneor more times to test different orientations and combinations ofelectrodes 344 until a threshold efficacy is indicated.

The catheters shown in FIGS. 17A and 17B may, in some examples, act aspermanent components deployed along with cylindrical lead members,instead of temporary delivery components that are used to arrange anddeploy the lead members and are thereafter removed. For example, thecatheters and the cylindrical lead members may be arranged within ablood vessel such that the catheter abuts and thereby is fixed withinthe lumen of the blood vessel. In such examples, the cylindrical leadmember may be rotated within the catheter to vary electrode orientationand combinations. The lead member may remain in an expanded stateabutting a lumen of the catheter from initial implantation until chronicdeployment, or, in other examples, may contract to be reoriented andexpand to test the new electrode orientation and/or combination. In anyevent, the catheters may remain deployed along with the cylindrical leadmembers within the blood vessel for chronic treatment of a patient.

FIGS. 18A-18D are schematic illustrations of different examples of acylindrical lead member that is expandable and contractible fordeployment and redeployment within jugular vein 158 of patient 12. FIGS.18A and 18B show mesh stent lead member 350 with different electrodeconfigurations, while FIGS. 18C and 18D show two different helical leadmembers 352 and 354 respectively. In FIGS. 18A and 18B, mesh stent leadmember 350 includes a plurality of material segments 356 each of whichis pivotally joined at either end to another segment at a vertex.Material segments 356 may be constructed from various biocompatiblematerials that resists corrosion and degradation from bodily fluidsincluding, e.g., titanium or biologically inert polymers. Generallyspeaking, mesh stent lead member 350 is expandable and contractible byrotation of material segments 356 with respect to each other at theplurality of vertices at which the segments are pivotally joined. Asmesh stent lead member 350 contracts, material segments 356 rotate suchthat the angle of each segment with respect to a longitudinal axis oflead member 350 decreases, which in turn decreases the diameter andincreases the overall length of the lead member. Conversely, as meshstent lead member 350 expands, material segments 356 rotate such thatthe angle of each segment with respect to the longitudinal axis of leadmember 350 increases, which in turn increases the diameter and decreasesthe overall length of the lead member. Other examples according to thisdisclosure may include stent lead members having differentconfigurations than lead member 350 of FIGS. 18A and 18B. For example,in one example, a mesh stent member may include fewer or more materialsegments pivotally joined at fewer or more vertices to form coarser orfiner meshes than mesh stent lead member 350. In another example, astent lead member may be constructed from a polymer that is expandableto take the shape of the blood vessel in which it is arranged. In stillanother example, a mesh stent member may include a resorbable materialinterconnecting some or all of the mesh that would, over a period oftime leave only the mesh of material segments and electrodes within theblood vessel of the patient.

FIGS. 18A and 18B illustrate stent lead member 350 with differentelectrode configurations. In FIG. 18A, electrodes 302 are connected tolead member 350 substantially coincident with the vertices at whichmaterial segments 356 are joined. In other examples, only some of thejunctions between material segments 356 may include electrodes 302arranged thereon or about. Electrodes 302, as illustrated in FIG. 18A,may protrude from the exterior surface of lead member 350, or any othercylindrical lead member according to this disclosure. In this manner,electrodes 302 may penetrate the wall of the blood vessel lumen in whichlead member 350 is arranged, e.g. jugular vein 158, to assist in fixingthe lead member within the vessel. In FIG. 18B, on the other hand, lead29 is wrapped partially or completely around stent lead member 350 andincludes ring electrodes 358 attached thereto. Wrapping lead 29 aroundlead member 350 along a helical trajectory as shown in FIG. 18B mayprovide a mechanical advantage for expansion of the lead member,because, in such an orientation, lead 29 may not need to stretch as theoverall length of lead member 350 increases.

FIGS. 18C and 18D show two different helical lead members 352 and 354respectively. Lead member 352 is a helical wire, while lead member 354is a helical ribbon. Both wire and ribbon helical lead members 352 and354 include electrodes 302 electrically connected to lead 29 andarranged generally in one or more lines parallel to the helicaltrajectory of each lead member. Generally speaking, helical lead members352 and 354 are expandable and contractible by bringing their respectiveends 352A, 352B and 354A, 354B closer together or further apart. In thecase of helical wire lead member 352, as ends 352A and 352B are broughtcloser together, individual windings of the helical wire are alsobrought closer together and the diameter of the helix of lead member 352expands. Conversely, as ends 352A and 352B are brought further apart,individual windings of the helical wire are also brought further apartand the diameter of the helix of lead member 352 contracts. In the caseof helical ribbon lead member 354, as ends 354A and 354B are broughtcloser together, helical slot 360 closes and the diameter of the helixof lead member 354 expands. Conversely, as ends 354A and 354B arebrought further apart, helical slot 360 is opened and the diameter ofthe helix of lead member 354 contracts.

Cylindrical lead members employed in examples according to thisdisclosure, in general, may include several additional features. In someexamples, a lead member may include a non-conductive material thatinsulates non-targeted tissue from stimulation pulses delivered by oneor more electrodes connected to the lead member or otherwise isolatesone or more electrodes from, e.g., other parts of the lead member. Inaddition to employing electrodes that protrude from the exterior surfaceof a cylindrical lead member to assist in fixation within a vessel (see,e.g., FIG. 18A), the lead member may include an abrasive or otherwisecoarse exterior surface or a drug-eluting coating that promotes tissuegrowth around the lead member, e.g. promotes fibrosis. Conversely, inother examples, a cylindrical lead member according to this disclosuremay include a drug-eluting coating that inhibits tissue growth, such asfibrosis to, e.g., increase the long term period over which thecylindrical member may be redeployed within a blood vessel.Additionally, in some examples, a cylindrical lead member may include adrug-eluting coating that prevents or inhibits stenosis of the bloodvessel in which it is arranged. In other examples, the cylindrical leadmember may include a number microhooks or small barbs arranged on anexterior surface to hold the lead member in place within the bloodvessel.

Cylindrical lead members according to this disclosure may also bedeployed and redeployed with the assistance of, e.g. a cup and releaseplate that receive one end of the lead member and serve to retain thelead member in place when, e.g., a sheath is retracted to temporarily orchronically deploy the lead member in a blood vessel. In some examples,the cup may be relatively deep to encapsulate a large longitudinallength of a proximal end of the lead member that is configured to expandto deploy the lead member. The cup may hold and encapsulate the proximalend of the lead member while a sheath extends over and encapsulates thelead member and the cup prior to deployment and after the sheath isretracted. After the sheath is retracted to partially deploy the leadmember, e.g., allow the distal end to expand in the blood vessel, thesheath may then either be extended again to redeploy the cylindricallead member, or the release plate may be extended to push out andthereby release and deploy the proximal end of the cylindrical memberfrom the cup. Other examples and a more detailed explanation ofdeployment mechanisms including such cup arrangements are described inU.S. Patent Publication No. 2007/0043420 A1 to Timothy W. Lostetter,filed on Aug. 17, 2005 and entitled “APPARATUS AND METHOD FORSTENT-GRAFT RELEASE USING A CAP,” the entire content of which isincorporated herein by this reference.

In some examples, a cylindrical lead member may include an electricalstimulator and, in some cases, need not be coupled to an implantablemedical device via a lead. In such examples, the electrical stimulatoron, within or attached to the cylindrical lead member may be powered byradio frequency pulses delivered from either an external or asubcutaneously implanted RF transmitter to a receiver unit arranged withthe stimulator or cylindrical lead member. In other examples, some partof the stimulator or cylindrical lead member may be composed of apiezoelectric material that can generate current when excitedmechanically by ultra sound waves transmitted from an external orimplanted source.

Similar to intravascular techniques, transvascular lead placementproximate a target nerve tissue site generally requires minimallyinvasive surgical techniques because the leads are guided to the sitethrough a blood vessel, e.g., a vein or artery that may be readilyaccessible, e.g., transcutaneously through a small incision. Unlikeintravascular, however, transvacular techniques guide the lead adjacentthe target tissue site and then pierce the vessel wall to arrange thelead and electrodes outside of the vessel adjacent the nerve tissue atwhich therapy is directed. Transvascular lead placement techniquesaccording to this disclosure provide for lead placement relative to thetarget nerve tissue and neighboring blood vessels to improve thetherapeutic effects of electrical stimulation provided to the patient bylead electrodes. Additionally, guided transvascular lead placement asdescribed herein may avoid safety risks of such procedures including,e.g., piercing adjacent vessels, such as an artery. The disclosedtransvascular techniques generally include improving lead placement bylocating target nerve tissue with a sensor, such as an IVUS imagingsystem, through a blood vessel adjacent the target tissue. After aplacement location is determined, one or more leads including one ormore electrodes may be deployed through the vessel wall and anchored tothe vessel wall or other tissue near the target nerve tissue.

Transvascular techniques generally include improving lead placement bylocating target nerve tissue with a sensor including, e.g., an IVUSimaging system through a blood vessel adjacent the target tissue. Afteran optimal placement location is determined relative to the nerve tissuewith the assistance of the tissue sensor, one or more leads includingone or more electrodes may be deployed through the vessel wall andanchored to the vessel wall or other tissue near the target nervetissue.

FIGS. 18 and 19 illustrate examples of transvascular lead placementtechniques in the context of vagal nerve stimulation in a human patient.FIG. 19 is a schematic illustration depicting lead 29 transvascularlyplaced adjacent vagus nerve 150 outside of internal jugular vein 158 inpatient 12. After or during placement, lead 29 may be connected to IMD16 or INS 26 similar to lead 28 shown in FIGS. 1A and 1B respectively.FIG. 20 is a flow chart illustrating an example method of placing lead29 in accordance with the example of FIG. 19. The example method of FIG.20 includes deploying a delivery catheter through a lumen of a bloodvessel to a target nerve tissue site (380), identifying a location ofthe nerve tissue with respect to the blood vessel with one or moresensors connected to the delivery catheter (382), advancing anelectrical stimulation electrode from the catheter through a wall of theblood vessel toward the nerve tissue (384), and energizing the electrodeto deliver electrical stimulation to the nerve tissue (386). One exampleof the method illustrated in FIG. 20 will be described in the context ofthe example lead placement structure shown in FIG. 19.

The arrangement shown in FIG. 19 includes delivery catheter 220, sensor222, deployment member 224, and spline 370. Sensor 222 is connected tocatheter 220 toward a distal end thereof. Deployment member 224 isextendable and retractable from catheter 220. Spline 370 is alsoconnected to a distal end of catheter 220 and is deployable to stabilizethe catheter within jugular vein 158. Sensor 222 is arranged between thedistal end of catheter 220 and the location along catheter 220 fromwhich deployment member 224 is extendable and retractable. Deploymentmember 224 includes tubular member 226, lead 29, electrode 228, andguidewire 230. Guidewire 230 includes anchor portion 230A at a distalend thereof. Electrode 228 is connected toward a distal end of lead 29.Lead 29 and guidewire 230 are received within and advanceable through alumen of tubular member 226. Lead 29 is advanceable along guidewire 230.

In FIG. 19, catheter 220 is deployed through internal jugular vein 158of patient 12 to a target nerve tissue stimulation site. In otherexamples, catheter 220 may be deployed in other blood vessels withinpatient 12 including, e.g., carotid artery 160, or the superior orinferior vena cava. Catheter 220 can be any suitable delivery cathetercapable of intravenous delivery within patient 12 and adapted toaccommodate sensor 222 and deployment member 224. Sensor 222 isconnected to the distal end of catheter 220 and is configured to detectthe position of vagus nerve 150 relative to jugular vein 158. Sensor222, in general, may be any suitable imaging or guidance systemincluding, e.g., a fiberoptic endoscope, ultrasound imaging system, orany other on-board imaging system capable of positioning catheter 220 toadvance electrode 228 through jugular vein 158 toward vagus nerve 150 byproviding an image of the area adjacent the location of sensor 222 oncatheter 220. In some examples, sensor 222 could be an array ofreceivers in relationship to a transmitter that provide an image ofsurrounding tissue and structures including vagus nerve 150 and carotidartery 160. In other examples, sensor 222 may be configured to send orreceive signals to or from any of a series of known signal generatorsincluding sonic, electromagnetic, light or radiation signals. In stillother examples, sensor 222 may be an optical oxygen content sensor thatmay be used to ensure that lead 29 and electrode 228 are not directedtoward, e.g., carotid artery 160 during lead placement. In someexamples, sensor 222 may be employed in conjunction with one or moreopaque markers viewable with fluoroscopic techniques or with anirrigated lumen that dispenses contrast media to assist in imaging theposition of vagus nerve 150 relative to jugular vein 158. In still otherexamples, sensor 222 may employed in addition to a separate opticaloxygen content or venous biomarker sensor that may be used to ensurethat lead 29 and electrode 228 are not directed toward, e.g., carotidartery 160 during lead placement. In some such examples, an opticaloxygen content or venous biomarker sensor may be connected to deploymentmember 224 to detect the presence of and reduce the risk of piercing orotherwise damaging carotid artery 160 as deployment member 224 includingelectrode 228 is advanced through the wall of the lumen of jugular vein158 toward vagus nerve 150.

In one example, sensor 222 is an intravenous ultrasound (“IVUS”) imagingsystem that is adapted to radiate ultrasonic waves out from sensor 222to generate a two dimensional image of the tissue and structuressurrounding catheter 220 and sensor 222. When activated, sensor 222 mayproduce an imaging field from ultrasonic waves produced by and radiatingradially from catheter 220 and sensor 222 (see, e.g., FIG. 11). The sizeof the imaging field may vary depending on the particular configurationand capabilities of sensor 222. The tissues and other structures caughtwithin the imaging field of sensor 222 may be distinguished from oneanother and the relative positioning of the different structures may bediscerned. Therefore, in the context of transvacular lead placement,vagus nerve 150, jugular vein 158, and carotid artery 160 may be caughtwithin the imaging field of sensor 222 to detect, e.g., the position ofnerve 150 relative to vein 158.

After sensor 222 identifies the location of vagus nerve 150 with respectto jugular vein 158, deployment member 224 including electrode 228 maybe advanced through the wall of the lumen of jugular vein 158 towardvagus nerve 150. Deployment member 224, in general, is extendable andretractable from catheter 220 from, e.g., an aperture formed in asidewall thereof. Deployment member 224 includes tubular member 226,lead 29, electrode 228, and guidewire 230. Tubular member 226 may be anystructure including at least one lumen through which various electrodedeployment structures including, e.g., lead 29 and guidewire 230 may beadvanced to place an electrode outside of vein 158 adjacent vagus nerve150. In the example of FIG. 19, tubular member 226 may be a needlecapable of piercing the wall of the lumen of vein 158 and including alumen in which lead 29 and guidewire 230 are received and through whichthe same are advanceable. Electrode 228 is connected to lead 29, whichis advanceable along guidewire 230.

With the aid of sensor 222, deployment member 224 is advanced fromcatheter 220 through jugular vein 158 toward vagus nerve 150. Lead 29,to which electrode 228 is connected, and guidewire 230 may be advancedthrough a lumen of deployment member 224 to position electrode 228outside of vein 158 adjacent vagus nerve 150. Guidewire 230 includesanchor portion 230A at a distal end thereof that is configured to anchordeployment member 224, lead 29 and electrode 228, and guidewire 230 totissue outside of vein 158. In the example of FIG. 19, anchor portion230A includes guidewire 230 formed in a spiral that is configured to betwisted tissue adjacent vagus nerve 150. Anchor portion 230A can befreed from the tissue by either untwisting guidewire 230, or in the casethat guidewire 230 is sufficiently flexible, pulling the wire away fromthe spiraling anchor portion 230A to effectively unwind and release theanchor from the tissue.

Having deployed catheter 220, detected the location of vagus nerve 150relative to jugular vein 158, and advanced electrode 228 through vein158 toward vagus nerve 150, electrical stimulation may be delivered tovagus nerve 150 via electrode 228. A portion of lead 29 extending awayfrom a distal end toward which electrode 228 is arranged may be guidedto connect with IMD 16. In one example, lead 29 may be guidedintravascularly to an implantation location of IMD 16 within patient 12.In other examples, at least a portion of lead 29 may be tunneled throughtissue of patient 12 to be connected to IMD 16. Although the example ofFIGS. 18 and 19 is described with reference to implanted medical device16 arranged within patient 12, examples according to this disclosurealso include lead 29 connected transcutaneously to an external medicaldevice that is configured to deliver electrical stimulation to thetarget nerve tissue, e.g., vagus nerve 150. After lead 29 is placedadjacent vagus nerve 150 outside of jugular vein 158 and connected toIMD 16, IMD 16, either automatically or as partially or completelycommanded by programmer 24, may deliver electrical stimulation therapyto and/or receive sensor feedback from vagus nerve 150 through electrode228.

In the example of FIGS. 18 and 19, as well as other examples disclosedherein, the efficacy of the electrical stimulation delivered byelectrode 228 to vagus nerve 150 may be compared to a threshold efficacyto determine whether or not electrode 228 is satisfactorily positionedwith respect to nerve 150. Efficacy may be measured, in general, byverbal feedback from patient 12, clinician observation of variousconditions of patient 12, or sensory feedback from one or more devicesincluding, e.g., ICD 17 shown in FIG. 1A or cardiac therapy module 104shown in FIG. 4. For example, to determine the response to stimulationof vagus nerve 150, ECG, heart rate, blood pressure, blood flow, cardiacoutput, and/or breathing, of patient 12 can be sensed or observed. Inanother example, efficacy may be measured by a sensor including, e.g.,an accelerometer that determines if stimulation of the neck muscles orphrenic nerve of patient 12 is occurring with or instead of stimulationof vagus nerve 150.

FIGS. 21A-21D show several alternative examples of deployment member 224for use in methods and systems according to this disclosure. In general,FIGS. 21A-21D show different arrangements and combinations of anchoringmembers and electrodes with respect to tubular member 226, lead 29, andguidewire 230 of deployment member 224. In the interest of simplicity,catheter 220 has been omitted from the illustrations of FIGS. 21A and21B. In FIG. 21A, deployment member 224 is advanced through the lumenwall of jugular vein 158 toward vagus nerve 150 and includes tubularmember 226, lead 29, electrode 228, guidewire 230, and expandable member390. In some examples, it may be desirable or necessary to useexpandable member 390 to enlarge the tract along which tubular member226 and guidewire 230 are advanced through and outside vein 158 prior toplacing lead 29 and electrode 228. In one example employing expandablemember 390, tubular member 226 and guidewire 230 may be advanced throughthe lumen wall of jugular vein 158 toward vagus nerve 150. Thereafter,expandable member 390 may be advanced over guidewire 230 and used toenlarge the tract along which lead 29 and electrode 228 will beadvanced. The expandable member 390 may, in some examples, be a ballooncatheter including, e.g., an angioplasty catheter. Instead of or inaddition to expandable member 390, other tract enlarging devices may beemployed including, e.g., electrosurgical debulking devices or tissuecutting devices.

In addition to or in lieu of tract enlargement, in some examples,expandable member 390 may provide additional stabilization or biasing oflead 29 or other components of deployment member 224 outside of jugularvein 158 adjacent vagus nerve 150. For example, expandable member 390may push against the exterior surface of jugular vein 158 as shown inFIG. 21A to bias lead 29 and electrode 228 toward vagus nerve 150. Inanother example, expandable member 390 may further stabilize theplacement of lead 29 and electrode 228 by expanding to apply force onjugular vein 158 and vagus nerve 150.

FIG. 21B shows deployment member 224 with anchor 392. In FIG. 21B,deployment member 224 is advanced through the lumen wall of jugular vein158 toward vagus nerve 150 and includes tubular member 226, lead 29,electrode 228, guidewire 230, and anchor 392. Anchor 392 is connected tolead 29 and is configured to secure lead 29 and thereby electrode 228 totissue outside of jugular vein 158 adjacent nerve 150. Anchor 392 may beany number of structures that are actively or passively deployable fromwithin tubular member 226 to engage tissue within patient 12. In theexample of FIG. 21B, anchor 392 is in the form of passive tines or barbsthat protrude from lead 29 and that may engage tissue outside of jugularvein 158 after lead 29 is advanced through and out of tubular member226. In other examples, anchor 392 may come in different shapes andsizes including, e.g., helical coils, C-shaped members, harpoon-likestructures, hooks, expandable or serrated members, and the like. In FIG.21B, anchor 392 is employed in lieu of anchor portion 230A of guidewire230. However, in other examples both anchor 392 and anchor portion 230Amay be used to securely deploy lead 29 and electrode 228 outside ofjugular vein 158 adjacent vagus nerve 150.

The anchors illustrated in FIGS. 14A-14J and described with reference tointravascular lead placement techniques may also be used intransvascular techniques disclosed herein. One or more of the anchorsillustrated in FIGS. 14A-14J may be employed, for example, alone or incombination in a manner as described with reference to anchor portion230A of guidewire 230 in FIG. 19. In such examples, anchor portion 230Aof guidewire 230 may take an alternative form to that shown in FIG. 19including, e.g., the harpoon anchors of FIGS. 14B and 14C. In anotherexample, one of the illustrated anchors of FIGS. 14A-14J may be employedas anchor 392 shown in FIG. 21B.

FIG. 21C shows catheter 220 with additional electrode 394 and deploymentmember 224 with additional electrode 396 connected to tubular member226. In FIG. 21C, deployment member 224 is advanced through the lumenwall of jugular vein 158 toward vagus nerve 150 and includes tubularmember 226, lead 29, electrode 228, guidewire 230, and additionalelectrodes 394, 396. Although transvascular placement examples of lead29 have been described herein with reference to a single electrode 228for simplicity, in practice, lead 29 will commonly include a pluralityof electrodes that may be employed in different anode and cathodecombinations to stimulate vagus nerve 150 as, e.g., described withreference to electrodes 80-83 in FIG. 2.

Additionally and as illustrated in FIG. 21C, catheter 220 may includeelectrode 394 in addition to lead electrode 228. In the example of FIG.21C, deployment member 224 may be advanced through the wall of jugularvein 158 and thereafter used to pull catheter 220 and electrode 394toward the lumen wall within jugular vein 158. For example, deploymentmember 224 may include an active or passive anchor (e.g. anchor portion230A of FIG. 21A, or anchor 392 of FIG. 21B) that fixes deploymentmember 224 outside of vein 158 adjacent vagus nerve 150. Afterdeployment member 224 is anchored outside of jugular vein 158, catheter220 may be pulled along deployment member 224 to abut the wall of thelumen of jugular vein 158 as shown in FIG. 21C, thereby positioningelectrode 394 within the vein proximate vagus nerve 150.

Deployment member 224 may also include electrodes in addition to leadelectrode 228 arranged in different locations and/or connected todifferent components. In FIG. 21C, electrode 396 is connected to tubularmember 226. In some examples, tubular member 226 and electrode 396 maybe advanced through the wall of vein 158 toward vagus nerve 150 prior tochronically deploying lead 29 and electrode 228. In such examples,electrode 396 may be used to deliver test stimulation pulses to vagusnerve 150 to determine the efficacy of the placement of deploymentmember 224 outside of jugular vein 158 with respect to vagus nerve 150.After determining a position of deployment member that provides athreshold efficacy in stimulating vagus nerve 150, lead 29 and guidewire230 may be advanced through tubular member 226 and lead 29 and electrode228 may be chronically deployed along the wall of the lumen of jugularvein 158 adjacent vagus nerve 150.

FIG. 21D shows guidewire 230 and lead 29 deployed transvascularly tocreate a cuff arrangement that wraps around vagus nerve 150. In FIG.21D, deployment member 224 is advanced through the lumen wall of jugularvein 158 toward vagus nerve 150 and includes tubular member 226, lead29, electrode 228, and guidewire 230. In some examples, it may bedesirable to anchor and/or localize the stimulation field delivered byelectrodes connected to lead 29 around the nerve. In one example, acurved member may be deployed from tubular member 226 to loop andthereby create a cuff around vagus nerve 150. The curved member may be,e.g., a tubular needle adapted to receive guidewire 230 and/or lead 29.In the example of FIG. 21D, the curved member is guidewire 230, which isadvanced from tubular member 226 of deployment member 224 around vagusnerve 150. After guidewire 230 is arranged around nerve 150, lead 29 andelectrode 228 may be advanced along the guidewire to wrap around thenerve.

In certain applications, transvascular lead placement may carry certaininherent risks. In some examples, advancing medical leads from within alumen of a blood vessel, through a wall of the vessel to place the leadsadjacent nerve tissue in an extravascular space may carry the risk ofpiercing or otherwise damaging other neighboring biological structuresincluding, e.g., other blood vessels. In the context of vagal nervestimulation/sensing examples disclosed herein, for example,transvascularly placing a lead adjacent vagus nerve 150 may carry therisk of piercing or otherwise causing damage to carotid artery 160adjacent the nerve and jugular vein 158. Therefore, in some examplesaccording to this disclosure, transvascular lead placement techniquesmay employ a deployment member part or all of which is constructed froma shape memory material such that the deployment member is configured topass laterally through a vessel wall and turn outside of the vessel tobe arranged longitudinally along the vessel adjacent the target nervetissue. In this way, the deployment member and other components of thetransvascular lead placement apparatus may reduce the risk of advancingtoo far laterally from the blood vessel and, e.g., piercing an adjacentvessel such as an artery.

FIG. 22 shows one example of deployment member 224 employing tubularmember 226 constructed from a shape memory material. Examples disclosedherein may use a variety of shape memory materials including, e.g.,nickel titanium (NiTi) alloys. NiTi is a shape memory alloy, which issometimes referred to as Nitinol. Other shape-memory alloys may also beused in examples disclosed herein including, e.g., copper tin (CuSn),indium titanium (InTi), and manganese copper (MnCu) alloys. Areversible, solid phase transformation known as martensitictransformation is the physical mechanism that underpins shape memorymaterials. Generally speaking, shape memory materials form a crystalstructure that can undergo a change from one crystal form to anotherinitiated by a temperature change or application of force. Above itstransformation temperature, Nitinol, e.g., is superelastic, able towithstand a small amount of deformation when a load is applied andreturn to its original shape when the load is removed. Below itstransformation temperature, it displays the shape memory effect. When itis deformed it will remain in that shape until heated above itstransformation temperature, at which time it will return to its originalshape. Nitinol is typically composed of approximately 50 to 55.6% nickelby weight. However, small changes in material composition can change thetransition temperature of the alloy significantly. As such, Nitinol mayor may not be superelastic at room temperature. The flexibility andunique properties of Nitinol to be used in a wide range of temperaturesmakes it suitable for many applications, particularly in medicine.

In FIG. 22, deployment member 224 includes tubular member 226, lead 29,electrode 228, and guidewire 230. Tubular member 226 may be anystructure including at least one lumen through which various electrodedeployment structures including, e.g., lead 29 and guidewire 230 may beadvanced to place an electrode outside of vein 158 adjacent vagus nerve150. In the example of FIG. 22, tubular member 226 may be a needlecapable of piercing the wall of the lumen of vein 158 and including alumen in which lead 29 and guidewire 230 are received and through whichthe same are advanceable. Electrode 228 is connected to lead 29, whichis advanceable along guidewire 230.

Deployment member 224 is advanced from catheter 220 through jugular vein158 toward vagus nerve 150. Lead 29, to which electrode 228 isconnected, and guidewire 230 may be advanced through a lumen ofdeployment member 224 to position electrode 228 outside of vein 158adjacent vagus nerve 150. In the example of FIG. 22, tubular member 226is constructed from a shape memory material including, e.g., Nitonol andgenerally takes an S-shape after being advanced through the lumen offrom catheter 220 (shown in FIG. 19) through the wall of jugular vein158. The material properties and shape of tubular member 226 reduce therisk that the needle, or another component of deployment member 224 willadvance too far laterally from jugular vein 158 and, e.g., pierce orotherwise damage carotid artery 160. After tubular member 226 isadvanced through the wall of vein 158, guidewire 230 may be deployed andlead 29 and electrode 228 may be advanced along guidewire 230 to arrangeelectrode 228 adjacent vagus nerve 150.

In other examples according to this disclosure, other components ofdeployment member 224 may be constructed from a shape memory material.For example, guidewire 230 may, in addition to or in lieu of tubularmember 226, be constructed from a shape memory material including, e.g.,Nitonol. In some such examples, tubular member 226 of deployment member224 is advanced from catheter 220 toward vagus nerve 150. Lead 29, towhich electrode 228 is connected, and guidewire 230 may be advancedthrough a lumen of tubular member 226 to position electrode 228 outsideof vein 158 adjacent vagus nerve 150. In particular, guidewire 230 isconstructed from a shape memory material and generally takes an S-shapeto pass out of tubular member 226, through the wall of vein 158, and runlongitudinally along and adjacent to vagus nerve 150 outside of vein158. After guidewire 230 is advanced through the wall of vein 158, lead29 and electrode 228 may be advanced along guidewire 230 to arrangeelectrode 228 adjacent vagus nerve 150.

The extra, intra, and transvascular lead placement techniques disclosedherein may benefit, in some examples, from electrode pairs arranged inflanking, non-contacting relationship with the target nerve tissue. Inone example, multiple leads are arranged longitudinally on opposingsides of and including electrodes in non-contacting relationship withthe target nerve tissue. In another example, a single lead includingmultiple electrodes is arranged such that at least two of the electrodesare arranged on opposing sides of and in non-contacting relationshipwith the target nerve tissue. Such flanking, non-contacting electrodearrangements may provide one or more anode and cathode electrodecombinations for electrical stimulation across the target nerve tissuewithout the deleterious effects of tissue contacting techniques, such asmay be caused by, e.g., cuff electrodes.

FIGS. 23A and 23B illustrate example arrangements of electrode pairs inflanking, non-contacting relationship with vagus nerve 150. The exampleof FIG. 23A includes multiple leads and may be applicable to differentcombinations of intra, extra, and transvascular lead placementtechniques disclosed herein. The example of FIG. 23B includes a singlelead including a pair of electrodes in flanking, non-contactingrelationship with vagus nerve 150. The example of FIG. 23B may begenerally applicable to extra and transvascular lead placementtechniques according to this disclosure.

The example of FIG. 23A includes leads 400 and 402, and electrodes 228.In FIG. 23A, Lead 400 is arranged longitudinally along one side of vagusnerve 150. Lead 402 is arranged longitudinally along a generallyopposing side of vagus nerve 150 across from lead 400. Each of leads 400and 402 include a plurality of electrodes 228 connected to the distalend of each lead. In the example of FIG. 23A, each lead 400 and 402includes four electrodes 228. However, in other examples, leads 400, 402may include fewer or more electrodes and may include different numbersof electrodes. Additionally, although FIG. 23A shows two leads 400, 402,other examples may include more than two leads including, e.g., four orsix leads, two of each of which are respectively arranged longitudinallyon opposing sides of and including electrodes in non-contactingrelationship with vagus nerve 150.

The example leads 400 and 402 shown in FIG. 23A may be placed withinpatient 12 according to different combinations of intra, extra, andtransvascular lead placement techniques disclosed herein. For example,lead 400 may be placed intravscularly within jugular vein 158 adjacentvagus nerve 150, while lead 402 is placed extravascularly within carotidsheath 156. In another example, lead 400 may be placed intravscularlywithin jugular vein 158 adjacent vagus nerve 150, while lead 402 isplaced transvascularly through the wall of vein 158 to an extravascularlocation adjacent the nerve. In still another example, both leads 400and 402 may be placed extravascularly within carotid sheath 156 adjacentvagus nerve 150. Similarly, both leads 400 and 402 may be placedtransvascularly through the wall of vein 158 to an extravascularlocation adjacent vagus nerve 150.

Pairs of electrodes 228 from leads 400, 402 may be employed to provideone or more anode/cathode combinations for electrical stimulation acrossvagus nerve 150. The neurostimulator or other device to which leads 400,402 are connected may include a switching module as described withreference to neurostimulation module 106 of IMD 16 in FIG. 2. Theswitching module may selectively couple pairs of electrodes 228 to asignal generator and/or sensing module to form different anode-cathodecombinations as indicated by dashed electrical field lines 404 in FIG.23A. The switching module may include, e.g., a switch array, switchmatrix, multiplexer, or any other type of switching device suitable toselectively couple stimulation energy to selected electrodes.

The example of FIG. 23B shows deployment member 224 that is configuredto be advanced and retracted from, e.g., a delivery catheter (not shownin FIG. 23B) through the wall of jugular vein 158 toward vagus nerve150. Deployment member 224 includes tubular member 226, lead 29, and apair of electrodes 228. Tubular member 226 may be any structureincluding at least one lumen through which various electrode deploymentstructures including, e.g., lead 29 and a guide member may be advancedto place an electrodes 228 in flanking, non-contacting relationship withvagus nerve 150. Electrodes 228 are connected to lead 29, which isadvanceable through tubular member along, e.g., a guide wire or stylus.In the example of FIG. 23B, lead 29 includes two electrodes 228.However, in other examples, lead 29 may include more electrodesincluding, e.g., four or six electrodes arranged in opposing pairs withrespect to vagus nerve 150.

Deployment member 224 is advanced through jugular vein 158 toward vagusnerve 150. Lead 29, to which electrodes 228 are connected, may beadvanced through a lumen of tubular member 226 to position one electrode228 inside jugular vein 158 and one electrode 228 outside of vein 158such that the two electrodes 228 flank vagus nerve 150 as shown in FIG.23B. In the example of FIG. 23B, lead 29 and electrodes 228 may beguided along, e.g., a guidewire that is constructed from a shape memorymaterial as described with reference to FIG. 22. Although the example ofFIG. 23B illustrates lead 29 and electrodes 228 placed transvascularly,other examples may include lead 29 placed extravascularly adjacent vagusnerve 150 in carotid sheath 156. After lead 29 and electrodes 228 areplaced with respect to vagus nerve 150, the pair of electrodes may beemployed to provide electrical stimulation across vagus nerve 150. Insome examples, the neurostimulator or other device to which lead 29 isconnected may include a signal generator and/or sensing module to coupleand energize electrodes 228 in anode-cathode combinations to stimulatevagus nerve 150 as indicated by dashed electrical field line 404 in FIG.23B.

Examples according to this disclosure generally provide medical leadplacement proximate nerve tissue within a patient for electricalstimulation of the tissue without the use of potentially deleteriouselectrode configurations including e.g., cuff electrodes. Techniquesdisclosed herein also generally provide flexible placement techniquesand structures by employing one or more temporary lead placements andstimulation tests, prior to chronically placing the leads within thepatient for nerve tissue stimulation. Furthermore, techniques accordingto this disclosure are adapted to enable minimally invasive introductionof the medical leads into the patient. Implantable electricalstimulation systems and methods in accordance with this disclosure maybe used to deliver therapy to patients suffering from conditions thatrange from chronic pain, tremor, Parkinson's disease, and epilepsy, tourinary or fecal incontinence, sexual dysfunction, obesity, spasticity,and gastroparesis. Specific types of electrical stimulation therapiesfor treating such conditions include, e.g., cardiac pacing,neurostimulation, muscle stimulation, or the like.

Various examples have been described in this disclosure. These and otherexamples are within the scope of the following claims.

The invention claimed is:
 1. A delivery system for deploying an implantable medical lead in a lumen of a blood vessel for stimulation of extravascular nerve tissue that is located adjacent to the blood vessel, via at least one electrode of the lead, the system comprising: an intravascular delivery catheter including a distal end, an aperture formed in a sidewall thereof to allow transverse passage out from the catheter, and a sensor located between the distal end and the aperture, the sensor adapted to radiate ultrasonic waves in order locate the extravascular nerve tissue, when the distal end of the catheter is inserted in the blood vessel lumen; a tubular member extendable and retractable from the catheter, via the aperture, the tubular member having a lumen configured to receive the implantable lead for advancing the lead out from the catheter and into the blood vessel lumen, when the tubular member is extended from the catheter; and a guidewire, along which the lead is advanceable, when the lead is received in the lumen of the tubular member, the guidewire being received within the lumen of the tubular member and advanceable therein, the guidewire including an anchor portion, the anchor portion being located at a distal end of the guidewire and distal to the lead, when the lead is advanced along the guidewire, the anchor portion being configured to temporarily anchor the guidewire to the wall of the blood vessel lumen, when the lead is advanced thereover and out from the catheter.
 2. The system of claim 1, wherein the tubular member further includes an electrode.
 3. The system of claim 1, wherein the nerve tissue comprises one of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve ganglia, and a vascular baroreceptor.
 4. A method for deploying, for chronic implant, an implantable medical lead to an intravascular location, the lead including at least one electrode for delivering stimulation to extravascular nerve tissue from the intravascular location, and the method comprising: deploying a delivery catheter through a lumen of a blood vessel to position a sensor of the catheter at a location in proximity to the nerve tissue, the sensor being located in proximity to a distal end of the catheter, between the distal end of the catheter and an aperture formed in a sidewall of the catheter; activating the positioned sensor of the catheter to generate an image of an area adjacent the distal end of the catheter and outside of the blood vessel, the image showing a position of the extravascular nerve tissue relative to the blood vessel; identifying the nerve tissue in the image generated by the activated sensor; rotating the catheter, after identifying the nerve tissue in the image, to orient the aperture of the catheter toward the identified nerve tissue; advancing the at least one electrode of the lead out from the oriented aperture of the catheter and toward the identified nerve tissue by advancing the lead over a guidewire, the guidewire being received in a lumen of a tubular member that extends out from the oriented aperture; actively fixing the advanced electrode to a wall of the blood vessel lumen that is adjacent the identified nerve tissue; energizing the fixed electrode to deliver stimulation; and comparing an efficacy of the delivered stimulation to a threshold efficacy.
 5. The method of claim 4, wherein actively fixing the electrode to the blood vessel wall comprises screwing a helical wire into the wall.
 6. The method of claim 4, wherein the nerve tissue comprises one of a vagus nerve, a hypoglossal nerve, a nerve plexus, nerve ganglia, and a vascular baroreceptor.
 7. The system of claim 1, wherein the anchor portion of the guidewire is formed in a spiral that is configured to be twisted into the lumen, when the guidewire is extended from the catheter.
 8. The method of claim 4, further comprising twisting a distal end of the guidewire into the wall of the blood vessel lumen to temporarily anchor the guidewire.
 9. The method of claim 4, further comprising delivering test stimulation pulses via an electrode of the tubular member, prior to advancing the at least one electrode of the lead. 